An Etymological Dictionary of Astronomy and Astrophysics

The eighth of → Saturn’s known → satellites, discovered by Herschel in 1789. It is about 500 km in diameter and orbits Saturn at a mean distance of 238,000 km with a period of 1.37 days. Enceladus has the highest → albedo (> 0.9) of any body in the → Solar System. Its surface is dominated by clean ice.

Geophysical data from the → Cassini-Huygens spacecraft imply the presence of a global → ocean below an ice shell with an average thickness of 20-25 km, thinning to just 1-5 km over the south polar region.

 There, → <i><a class="linkVoir" href="/terms/jet/">jet</a></i>s of
 → <i><a class="linkVoir" href="/terms/water-vapor/">water vapor</a></i> and icy grains are
 launched through fissures in the → <i><a class="linkVoir" href="/terms/ice/">ice</a></i>. 
 The composition of the ejected
 material measured by Cassini includes salts and silica dust.

In order to explain these observations, an abnormally high heat power is required, about 100 times more than is expected to be generated by the natural → decay of → radioactive elements in rocks in its core, as well as a means of focusing activity at the south pole.

According to simulations, the core is made of unconsolidated, easily deformable, porous rock that water can easily permeate. The → tidal friction from Saturn is thought to be at the origin of the eruptions deforming the icy shell by push-pull motions as the moon follows an elliptical path around the giant planet. But the energy produced by tidal friction in the ice, by itself, would be too weak to counterbalance the heat loss seen from the ocean; the globe would freeze within 30 million years.

More than 10 GW of heat can be generated by tidal friction inside the rocky core. Water transport in the tidally heated permeable core results in hot narrow upwellings with temperatures exceeding 90 °C, characterized by powerful (1-5 GW) hotspots at the seafloor, particularly at the south pole. The release of heat in narrow regions favors intense interaction between water and rock, and the transport of hydrothermal products from the core to the plume sources
(Choblet et al., 2017, Nature Astronomy, doi:10.1038/s41550-017-0289-8)

Etymology (EN): In Gk. mythology Enceladus was a Titan who battled Athene in their war against the gods. When he fled the battlefield, Athene crushed him beneath the Sicilian Mount Etna.

Etymology (PE): Enkelâdos, from the original Gk. pronunciation of the name.

The eighth of → Saturn’s known → satellites, discovered by Herschel in 1789. It is about 500 km in diameter and orbits Saturn at a mean distance of 238,000 km with a period of 1.37 days. Enceladus has the highest → albedo (> 0.9) of any body in the → Solar System. Its surface is dominated by clean ice.

Geophysical data from the → Cassini-Huygens spacecraft imply the presence of a global → ocean below an ice shell with an average thickness of 20-25 km, thinning to just 1-5 km over the south polar region.

 There, → <i><a class="linkVoir" href="/terms/jet/">jet</a></i>s of
 → <i><a class="linkVoir" href="/terms/water-vapor/">water vapor</a></i> and icy grains are
 launched through fissures in the → <i><a class="linkVoir" href="/terms/ice/">ice</a></i>. 
 The composition of the ejected
 material measured by Cassini includes salts and silica dust.

In order to explain these observations, an abnormally high heat power is required, about 100 times more than is expected to be generated by the natural → decay of → radioactive elements in rocks in its core, as well as a means of focusing activity at the south pole.

According to simulations, the core is made of unconsolidated, easily deformable, porous rock that water can easily permeate. The → tidal friction from Saturn is thought to be at the origin of the eruptions deforming the icy shell by push-pull motions as the moon follows an elliptical path around the giant planet. But the energy produced by tidal friction in the ice, by itself, would be too weak to counterbalance the heat loss seen from the ocean; the globe would freeze within 30 million years.

More than 10 GW of heat can be generated by tidal friction inside the rocky core. Water transport in the tidally heated permeable core results in hot narrow upwellings with temperatures exceeding 90 °C, characterized by powerful (1-5 GW) hotspots at the seafloor, particularly at the south pole. The release of heat in narrow regions favors intense interaction between water and rock, and the transport of hydrothermal products from the core to the plume sources
(Choblet et al., 2017, Nature Astronomy, doi:10.1038/s41550-017-0289-8)

Etymology (EN): In Gk. mythology Enceladus was a Titan who battled Athene in their war against the gods. When he fled the battlefield, Athene crushed him beneath the Sicilian Mount Etna.

Etymology (PE): Enkelâdos, from the original Gk. pronunciation of the name.

A region of decreased brightness within the A ring of Saturn.

Etymology (EN): In honor of Johann Franz Encke, → Encke’s comet. Gap, from O.N. gap “chasm,” related to gapa “to gape.”

Etymology (PE): Gâf, variant kâf “split, slit,” stem of kâftan, kâvidan “to split; to dig,” Mid./Mod.Pers. škâf- škâftan “to split, burst,” Proto-Iranian *kap-, *kaf- “to split;” cf. Gk. skaptein “to dig;” L. scabere “to scratch, scrape,” P.Gmc. skabanan (Goth. skaban;
Ger. schaben; E. shave). PIE base (s)kep- “to cut, to scrape, to hack.”

A region of decreased brightness within the A ring of Saturn.

Etymology (EN): In honor of Johann Franz Encke, → Encke’s comet. Gap, from O.N. gap “chasm,” related to gapa “to gape.”

Etymology (PE): Gâf, variant kâf “split, slit,” stem of kâftan, kâvidan “to split; to dig,” Mid./Mod.Pers. škâf- škâftan “to split, burst,” Proto-Iranian *kap-, *kaf- “to split;” cf. Gk. skaptein “to dig;” L. scabere “to scratch, scrape,” P.Gmc. skabanan (Goth. skaban;
Ger. schaben; E. shave). PIE base (s)kep- “to cut, to scrape, to hack.”

A faint comet with the shortest known period (about 3.30 years). Its semimajor axis is 2.21 AU and aphelion 4.1 AU. it is the parent body of the Taurids meteor shower. The comet was first observed in 1786 by the French astronomer Pierre Méchain.

See also: Named after the German astronomer Johann Franz Encke (1791-1865), who in 1819 computed its orbit and proved that sightings of apparently different comets in 1786, 1795, 1805, and 1818 were in fact appearances of the same comet. → comet.

A faint comet with the shortest known period (about 3.30 years). Its semimajor axis is 2.21 AU and aphelion 4.1 AU. it is the parent body of the Taurids meteor shower. The comet was first observed in 1786 by the French astronomer Pierre Méchain.

See also: Named after the German astronomer Johann Franz Encke (1791-1865), who in 1819 computed its orbit and proved that sightings of apparently different comets in 1786, 1795, 1805, and 1818 were in fact appearances of the same comet. → comet.

To convert (data, information) into another format by → encoding. See also → decode and → encrypt.

Etymology (EN): From en- “in; into” + → code.

Etymology (PE): Ramzândan, infinitive from ramz, → code. Ramz gozâštan, from ramz + gozâštan “to place, put,” → nomenclature.

To convert (data, information) into another format by → encoding. See also → decode and → encrypt.

Etymology (EN): From en- “in; into” + → code.

Etymology (PE): Ramzândan, infinitive from ramz, → code. Ramz gozâštan, from ramz + gozâštan “to place, put,” → nomenclature.

An electronic device or software program used to convert (a message, information, data) into a specialized digital format for efficient transmission or transfer.

See also: → encode; → -er.

An electronic device or software program used to convert (a message, information, data) into a specialized digital format for efficient transmission or transfer.

See also: → encode; → -er.

A process used for transforming data into another format by means of a scheme that is publicly available so that it can easily be reversed. See also → decoding and → encryption.

See also: → encode; → -ing.

A process used for transforming data into another format by means of a scheme that is publicly available so that it can easily be reversed. See also → decoding and → encryption.

See also: → encode; → -ing.

General: A meeting, especially one that is unplanned, unexpected, or brief. An often violent meeting; a clash.
Coming across of two bodies (as two stars in a cluster) which results in the deviation from
original directions of motion. → close encounter; → strong encounter; → weak encounter.

Etymology (EN): From O.Fr. encountrer “confront,” from encontre “against, counter to,” from L.L. incontra “in front of,” from L. in- “in” + contra “against.”

Etymology (PE): Ruyâruyi “being face to face,” from ru, ruy “face, countenance,” variant rox (Mid.Pers. rôy, rôdh “face,” Av. raoδa- “growth,” in plural “appearance,” from raod- “to grow, sprout, shoot,” cf. Skt. róha- “rising, height”) + euphonic interfix -â- + ruy + noun suffix -i.

General: A meeting, especially one that is unplanned, unexpected, or brief. An often violent meeting; a clash.
Coming across of two bodies (as two stars in a cluster) which results in the deviation from
original directions of motion. → close encounter; → strong encounter; → weak encounter.

Etymology (EN): From O.Fr. encountrer “confront,” from encontre “against, counter to,” from L.L. incontra “in front of,” from L. in- “in” + contra “against.”

Etymology (PE): Ruyâruyi “being face to face,” from ru, ruy “face, countenance,” variant rox (Mid.Pers. rôy, rôdh “face,” Av. raoδa- “growth,” in plural “appearance,” from raod- “to grow, sprout, shoot,” cf. Skt. róha- “rising, height”) + euphonic interfix -â- + ruy + noun suffix -i.

To convert (information or data) into a system of symbols, especially to prevent unauthorized access. See also → decrypt and → encode.

Etymology (EN): From en- “in; into” + L. crypt, from Gk. kryptos “hidden, concealed, secret” + → -tion.

Etymology (PE): Darnahândan, from dar-, → in- + nahândan “to hide, conceal,” from nahân “concealed, hid; clandestine;” Mid.Pers. nihân “secrecy, a secret place, a hiding place,” nihânik “concealed;” Av. niδāti- “deposing, deposit.”

To convert (information or data) into a system of symbols, especially to prevent unauthorized access. See also → decrypt and → encode.

Etymology (EN): From en- “in; into” + L. crypt, from Gk. kryptos “hidden, concealed, secret” + → -tion.

Etymology (PE): Darnahândan, from dar-, → in- + nahândan “to hide, conceal,” from nahân “concealed, hid; clandestine;” Mid.Pers. nihân “secrecy, a secret place, a hiding place,” nihânik “concealed;” Av. niδāti- “deposing, deposit.”

A process that transforms data into another format in such a way that only specific individual(s) can reverse the transformation. Encryption is for maintaining data confidentiality.

See also → decryption and → encoding.

See also: → encrypt; → -tion.

A process that transforms data into another format in such a way that only specific individual(s) can reverse the transformation. Encryption is for maintaining data confidentiality.

See also → decryption and → encoding.

See also: → encrypt; → -tion.

A combining form meaning “within, inside” used in the formation of compound terms such as → endomorphism and → endothermic.

Etymology (EN): From Fr., from Gk. endon “in, within, at home,” from en “in” + -don, base of domos “house,” → domain.

Etymology (PE): Darun “in, into, within;” Mid.Pers. andarôn “inside,” from andar, → inter- + rôn “side, direction;” Av. ravan- “(course of a) river.”

A combining form meaning “within, inside” used in the formation of compound terms such as → endomorphism and → endothermic.

Etymology (EN): From Fr., from Gk. endon “in, within, at home,” from en “in” + -don, base of domos “house,” → domain.

Etymology (PE): Darun “in, into, within;” Mid.Pers. andarôn “inside,” from andar, → inter- + rôn “side, direction;” Av. ravan- “(course of a) river.”

A nuclear or molecular process in which some of the energy of the incoming particle is absorbed by, or transferred to, the other particle.

Etymology (EN): → endo- + -ergic, a combining form with the meanings “activated by, sensitive to, releasing, resembling the effect produced by the substance or phenomenon specified by the initial element,” from → erg, → energy + → -ic;
→ process.

Etymology (PE): Farâravand, → process; kâružgir, from kâruž, → energy, + gir present stem of gereftan “to take, seize, catch” (Mid.Pers. griftan, Av./O.Pers. grab- “to take, seize,” cf.
Skt. grah-, grabh- “to seize, take,” graha “seizing, holding, perceiving,” M.L.G. grabben “to grab,” from P.Gmc. *grab, E. grab “to take or grasp suddenly;” PIE base *ghrebh- “to seize”).

A nuclear or molecular process in which some of the energy of the incoming particle is absorbed by, or transferred to, the other particle.

Etymology (EN): → endo- + -ergic, a combining form with the meanings “activated by, sensitive to, releasing, resembling the effect produced by the substance or phenomenon specified by the initial element,” from → erg, → energy + → -ic;
→ process.

Etymology (PE): Farâravand, → process; kâružgir, from kâruž, → energy, + gir present stem of gereftan “to take, seize, catch” (Mid.Pers. griftan, Av./O.Pers. grab- “to take, seize,” cf.
Skt. grah-, grabh- “to seize, take,” graha “seizing, holding, perceiving,” M.L.G. grabben “to grab,” from P.Gmc. *grab, E. grab “to take or grasp suddenly;” PIE base *ghrebh- “to seize”).

A → morphism from an → object to itself.

See also: → endo-; → morphism.

A → morphism from an → object to itself.

See also: → endo-; → morphism.

Process during which heat is absorbed by the system from outside.

Etymology (EN): → endo- + -therm, from Gk. therme “heat,” from PIE *ghwerm-/*ghworm- “warm;” cf. Pers. garm “warm,” L. fornax “an oven,” O.E. wearm “warm” + → -ic.

Etymology (PE): From garmâ “heat, warmth” (Mid.Pers. garm, O.Pers./Av. garəma- “hot, warm,” cf. Skt. gharmah “heat,” Gk. thermos “warm,” L. formus “warm,” P.Gmc. *warmaz, O.E. wearm, O.H.G., Ger. warm, PIE *ghworm-/*ghwerm-, as above) + gir present tense stem of gereftan “to take, seize, catch” (Mid.Pers. griftan, Av./O.Pers. grab- “to take, seize,” cf.
Skt. grah-, grabh- “to seize, take,” graha “seizing, holding, perceiving,” M.L.G. grabben “to grab,” from P.Gmc. *grab, E. grab “to take or grasp suddenly;” PIE base *ghrebh- “to seize”).

Process during which heat is absorbed by the system from outside.

Etymology (EN): → endo- + -therm, from Gk. therme “heat,” from PIE *ghwerm-/*ghworm- “warm;” cf. Pers. garm “warm,” L. fornax “an oven,” O.E. wearm “warm” + → -ic.

Etymology (PE): From garmâ “heat, warmth” (Mid.Pers. garm, O.Pers./Av. garəma- “hot, warm,” cf. Skt. gharmah “heat,” Gk. thermos “warm,” L. formus “warm,” P.Gmc. *warmaz, O.E. wearm, O.H.G., Ger. warm, PIE *ghworm-/*ghwerm-, as above) + gir present tense stem of gereftan “to take, seize, catch” (Mid.Pers. griftan, Av./O.Pers. grab- “to take, seize,” cf.
Skt. grah-, grabh- “to seize, take,” graha “seizing, holding, perceiving,” M.L.G. grabben “to grab,” from P.Gmc. *grab, E. grab “to take or grasp suddenly;” PIE base *ghrebh- “to seize”).

1. Remain in existence; last.
   

   2. Suffer (something painful or difficult) patiently (OxfordDictionaries.com).

Etymology (EN): From L. indurare “make hard,” from in- + durare “to harden,” from durus “hard,” → duration.

Etymology (PE): Pâyidan, → last (v.);
Tâb âvardan b"endure," from tâb “toleration, patience,” related to tavân, tavânestan “to be able,” → conserve, + âvardan “to bring, to cause, produce,” → production.

1. Remain in existence; last.
   

   2. Suffer (something painful or difficult) patiently (OxfordDictionaries.com).

Etymology (EN): From L. indurare “make hard,” from in- + durare “to harden,” from durus “hard,” → duration.

Etymology (PE): Pâyidan, → last (v.);
Tâb âvardan b"endure," from tâb “toleration, patience,” related to tavân, tavânestan “to be able,” → conserve, + âvardan “to bring, to cause, produce,” → production.

1. Having a relatively high amount of energy.
   

2. Of or relating to energy.

See also: → energy + -t + → -ic.

1. Having a relatively high amount of energy.
   

2. Of or relating to energy.

See also: → energy + -t + → -ic.

Electrons and atomic nuclei ejected by solar flares, travelling with velocities amounting to a fraction of the velocity of light, and energies mostly in the range 1-100 million → electronvolts (eV), but occasionally as high as 15 billion eVs.
Also known as solar → cosmic rays.

Etymology (EN): Energetic, from Gk. energetikos, from energe-,
→ energy, + -tikos a suffix, equivalent in meaning to → -ic, occurring in adjectives; → solar; → particle.

Etymology (PE): Zarrehâ plural of zarré, → particle;
xoršidi, → solar; kâružmand from kâruž, → energy, + -mand possession suffix.

Electrons and atomic nuclei ejected by solar flares, travelling with velocities amounting to a fraction of the velocity of light, and energies mostly in the range 1-100 million → electronvolts (eV), but occasionally as high as 15 billion eVs.
Also known as solar → cosmic rays.

Etymology (EN): Energetic, from Gk. energetikos, from energe-,
→ energy, + -tikos a suffix, equivalent in meaning to → -ic, occurring in adjectives; → solar; → particle.

Etymology (PE): Zarrehâ plural of zarré, → particle;
xoršidi, → solar; kâružmand from kâruž, → energy, + -mand possession suffix.

The total energy relations and transformations of energy within a particular physical, chemical, or biological system.

See also: → energy + -t + → -ics.

The total energy relations and transformations of energy within a particular physical, chemical, or biological system.

See also: → energy + -t + → -ics.

In physics, capacity for doing work.

Etymology (EN): From M.Fr. energie, from L.L. energia, from Gk. energeia “force in action, activity, operation,” from energos “active, working,” from en- “in, at” + ergon “work,” from PIE base *werg- “to work” (cf. Av. varəz- “to work, do, perform, exercise;” Mod.Pers. varz-, varzidan “to labor, exercise, practise;” Arm. gorc “work;” Lith. verziu “tie, fasten, squeeze,” vargas “need, distress;” Goth. waurkjan; O.E. wyrcan “work,” wrecan “to drive, hunt, pursue”).

Etymology (PE): Kâruž, literally “work strength,” from kâr + už. The first component kâr “work,” Mid.Pers kâr, Mod./Mid.Pers. kardan “to do, to work,” Mid.Pers. kardan; O.Pers./Av. kar- “to do, make, build,” Av. kərənaoiti “he makes;” cf. Skt. kr- “to do, to make,” krnoti “he makes, he does,”
karoti “he makes, he does,” karma “act, deed;” PIE base k^wer- “to do, to make.” The second component, už, from Mid.Pers. ôž “strength” (ôžômand “strong”), Av. aogah-, aojah- “strength” (aojahvant- “strong”) Skt. ojas- “strength” (ojasvant- “strong”); L. augustus “venerable,” L.L. augmentare “to increase,” from augere
“to increase, enlarge, enrich;” Lith. augu “to grow;” Gk. auxo “increase;” Goth. aukan “to grow, increase;” O.E. eacien “to increase”); PIE *augos- “force,” *aug- “to increase.”

In physics, capacity for doing work.

Etymology (EN): From M.Fr. energie, from L.L. energia, from Gk. energeia “force in action, activity, operation,” from energos “active, working,” from en- “in, at” + ergon “work,” from PIE base *werg- “to work” (cf. Av. varəz- “to work, do, perform, exercise;” Mod.Pers. varz-, varzidan “to labor, exercise, practise;” Arm. gorc “work;” Lith. verziu “tie, fasten, squeeze,” vargas “need, distress;” Goth. waurkjan; O.E. wyrcan “work,” wrecan “to drive, hunt, pursue”).

Etymology (PE): Kâruž, literally “work strength,” from kâr + už. The first component kâr “work,” Mid.Pers kâr, Mod./Mid.Pers. kardan “to do, to work,” Mid.Pers. kardan; O.Pers./Av. kar- “to do, make, build,” Av. kərənaoiti “he makes;” cf. Skt. kr- “to do, to make,” krnoti “he makes, he does,”
karoti “he makes, he does,” karma “act, deed;” PIE base k^wer- “to do, to make.” The second component, už, from Mid.Pers. ôž “strength” (ôžômand “strong”), Av. aogah-, aojah- “strength” (aojahvant- “strong”) Skt. ojas- “strength” (ojasvant- “strong”); L. augustus “venerable,” L.L. augmentare “to increase,” from augere
“to increase, enlarge, enrich;” Lith. augu “to grow;” Gk. auxo “increase;” Goth. aukan “to grow, increase;” O.E. eacien “to increase”); PIE *augos- “force,” *aug- “to increase.”

The → turbulent process whereby → kinetic energy is transformed into heat by the action of nonlinear coupling which transfers the energy from large eddies (→ eddy) to smaller and smaller eddies, finally arriving at → dissipative
scales dominated by → viscosity (direct cascade). In the simplest case (3D homogeneous hydrodynamic turbulence), the resulting energy distribution is the → Kolmogorov spectrum.
The reverse process also exists (inverse cascade) whereby energy is transferred to larger and larger eddies.

See also: → energy; → cascade.

The → turbulent process whereby → kinetic energy is transformed into heat by the action of nonlinear coupling which transfers the energy from large eddies (→ eddy) to smaller and smaller eddies, finally arriving at → dissipative
scales dominated by → viscosity (direct cascade). In the simplest case (3D homogeneous hydrodynamic turbulence), the resulting energy distribution is the → Kolmogorov spectrum.
The reverse process also exists (inverse cascade) whereby energy is transferred to larger and larger eddies.

See also: → energy; → cascade.

The amount of energy in the form of radiation per unit volume, expressed in ergs cm^-3. In particular, the energy density of blackbody radiation at temperature T is aT⁴, where the radiation constant a = 7.56 × 10^-15 erg cm^-3 (K)^-4.

See also: → energy; → density.

The amount of energy in the form of radiation per unit volume, expressed in ergs cm^-3. In particular, the energy density of blackbody radiation at temperature T is aT⁴, where the radiation constant a = 7.56 × 10^-15 erg cm^-3 (K)^-4.

See also: → energy; → density.

Of a stellar → nuclear fusion, the equation describing the → energy generation rate as a function of → density and → temperature.

See also: → energy; → generation; → equation.

Of a stellar → nuclear fusion, the equation describing the → energy generation rate as a function of → density and → temperature.

See also: → energy; → generation; → equation.

Of a stellar → nuclear fusion, the energy produced per unit mass per unit time, usually denoted ε (erg g^-1s^-1). The general form of the energy generation equation is: ε = ε₀ρ^λT^ν, where ε₀, ρ, and λ are constants over some efficiently restricted range of → temperature T, → density ρ, and → chemical composition. The temperature exponent ν is about 4, 15, and 40 for → proton-proton chain, → CNO cycle, and → triple alpha process, respectively.

See also: → energy; → generation; → rate.

Of a stellar → nuclear fusion, the energy produced per unit mass per unit time, usually denoted ε (erg g^-1s^-1). The general form of the energy generation equation is: ε = ε₀ρ^λT^ν, where ε₀, ρ, and λ are constants over some efficiently restricted range of → temperature T, → density ρ, and → chemical composition. The temperature exponent ν is about 4, 15, and 40 for → proton-proton chain, → CNO cycle, and → triple alpha process, respectively.

See also: → energy; → generation; → rate.

Any of the several discrete states of energy which a particle, atom, or molecule can adopt under conditions where the possible values are restricted by quantum mechanical laws.

See also: → energy; → level.

Any of the several discrete states of energy which a particle, atom, or molecule can adopt under conditions where the possible values are restricted by quantum mechanical laws.

See also: → energy; → level.

Of cosmic rays, the plot representing the number of particles as a function of their energy.

See also: → energy; → spectrum.

Of cosmic rays, the plot representing the number of particles as a function of their energy.

See also: → energy; → spectrum.

Same as → energy level.

See also: → energy; → state.

Same as → energy level.

See also: → energy; → state.

The → conversion of one → form of energy into another, or the movement of energy from one place or system to another.

See also: → energy; → transfer.

The → conversion of one → form of energy into another, or the movement of energy from one place or system to another.

See also: → energy; → transfer.

A tensor (T_μν) related to the → Einstein tensor through → Einstein’s field equations. The energy-momentum tensor depends upon the distribution of the → energy and → matter in the space.

See also: → energy; → momentum; → tensor.

A tensor (T_μν) related to the → Einstein tensor through → Einstein’s field equations. The energy-momentum tensor depends upon the distribution of the → energy and → matter in the space.

See also: → energy; → momentum; → tensor.

1. Any machine that converts energy, especially heat energy, into mechanical power or motion.
   

2. The part of a processor or software program that determines how the program manages and manipulates data. The term is most often used in relation to a specific task.

Etymology (EN): M.E. engin, from O.Fr. engin “skill, cleverness; war machine,” from L. ingenium “inborn qualities, talent,” from → in- “in”

• gen-, root of gignere “to beget, produce;” cognate with Pers. zâdan “to bring forth, give birth;” → generate.

Etymology (PE): Motor, loanword from Fr. moteur, from L. motor “mover,” from movere “to move.”

1. Any machine that converts energy, especially heat energy, into mechanical power or motion.
   

2. The part of a processor or software program that determines how the program manages and manipulates data. The term is most often used in relation to a specific task.

Etymology (EN): M.E. engin, from O.Fr. engin “skill, cleverness; war machine,” from L. ingenium “inborn qualities, talent,” from → in- “in”

• gen-, root of gignere “to beget, produce;” cognate with Pers. zâdan “to bring forth, give birth;” → generate.

Etymology (PE): Motor, loanword from Fr. moteur, from L. motor “mover,” from movere “to move.”

A person who designs, constructs, or works with engines or machines.

Etymology (EN): M.E. engin(e)our, from O.Fr. engigneor, from L.L. ingeniare, → engine.

Etymology (PE): Mohandes, from Ar. muhandis “measurer,” from Pers. andâzé, → measure.

A person who designs, constructs, or works with engines or machines.

Etymology (EN): M.E. engin(e)our, from O.Fr. engigneor, from L.L. ingeniare, → engine.

Etymology (PE): Mohandes, from Ar. muhandis “measurer,” from Pers. andâzé, → measure.

The action, work, or profession of an engineer.

See also: → engineer + → -ing.

The action, work, or profession of an engineer.

See also: → engineer + → -ing.

A method of mounting a telescope in which the polar axis is supported at each end by two piers. The great defect of this type of mounting is its inability to observe the pole.

See also: → mounting.

A method of mounting a telescope in which the polar axis is supported at each end by two piers. The great defect of this type of mounting is its inability to observe the pole.

See also: → mounting.

To raise to a higher degree; intensify; magnify (Dictionary.com).

Etymology (EN): M.E. enhauncen, from Anglo-Fr. enhauncer, from O.Fr. enhaucier “make higher, make greater; raise in esteem,” from V.L. *inaltiare, from L.L. inaltare “raise, exalt,” from altare “make high,” from altus “high.”

Etymology (PE): Bolandidan, from boland “high,” related to bâlâ “up, above, high, elevated, height,” borz, “height, magnitude,” → magnitude.

To raise to a higher degree; intensify; magnify (Dictionary.com).

Etymology (EN): M.E. enhauncen, from Anglo-Fr. enhauncer, from O.Fr. enhaucier “make higher, make greater; raise in esteem,” from V.L. *inaltiare, from L.L. inaltare “raise, exalt,” from altare “make high,” from altus “high.”

Etymology (PE): Bolandidan, from boland “high,” related to bâlâ “up, above, high, elevated, height,” borz, “height, magnitude,” → magnitude.

An increase or improvement in value, extent, or quality.

See also: Verbal noun of → enhance.

An increase or improvement in value, extent, or quality.

See also: Verbal noun of → enhance.

A puzzling or inexplicable occurrence or situation. See also: → problem, → puzzle.

Etymology (EN): From L. aenigma “riddle,” from Gk. ainigma “a dark saying, riddle,” from ainissesthai “speak obscurely, speak in riddles,” from ainos “tale, story; saying, proverb;” of unknown origin.

Etymology (PE): Câceh, from Baluci (Zâhedân) câcâk “riddle, puzzle;” cf.
(Kermânšâhi) câvca “riddle, puzzle” (Fin-e Bandar-Abbâs) cencen “riddle;” maybe related to Choresmian c’tyk “riddle,” from Proto-Ir. *caš- “to teach, to show;” Av. *caš- “to teach, to show” (Cheung 2007).

A puzzling or inexplicable occurrence or situation. See also: → problem, → puzzle.

Etymology (EN): From L. aenigma “riddle,” from Gk. ainigma “a dark saying, riddle,” from ainissesthai “speak obscurely, speak in riddles,” from ainos “tale, story; saying, proverb;” of unknown origin.

Etymology (PE): Câceh, from Baluci (Zâhedân) câcâk “riddle, puzzle;” cf.
(Kermânšâhi) câvca “riddle, puzzle” (Fin-e Bandar-Abbâs) cencen “riddle;” maybe related to Choresmian c’tyk “riddle,” from Proto-Ir. *caš- “to teach, to show;” Av. *caš- “to teach, to show” (Cheung 2007).

Resembling an enigma, or a puzzling occurrence, situation, statement, person, etc.; perplexing; mysterious (Dictionary.com).

Etymology (EN): → enigma; → -ic.

Etymology (PE): Cušenâk, from cušé, → enigma,

• -nâk adj. suffix.

Resembling an enigma, or a puzzling occurrence, situation, statement, person, etc.; perplexing; mysterious (Dictionary.com).

Etymology (EN): → enigma; → -ic.

Etymology (PE): Cušenâk, from cušé, → enigma,

• -nâk adj. suffix.

An intellectual movement in Europe during the 17th and 18th centuries celebrating human reason and scientific thought as the instruments of progress and subjecting conventional ways of thinking to rigorous critique.
The Enlightenment culminated with the writings of Jean-Jacques Rousseau (1712-1778) and the Encyclopédistes, the philosophy of Immanuel Kant (1724-1804), and the political ideals of the French and American Revolutions, while the precursor in science and philosophy included Francis Bacon (1561-1626), René Descartes (1596-1650), Isaac Newton (1643-1727), John Locke (1632-1704), and Thomas Hobbes (1588-1679).

Etymology (EN): From enlighten, from en- + → light + -en

• → -ment.

Etymology (PE): Asr, → age; rowšangari, noun from rowšangar “enlightener,” from rowšan “light, bright, luminous, splendid,” cognate with L. lux, → bright, + -gar a suffix of agent nouns, → -or.

An intellectual movement in Europe during the 17th and 18th centuries celebrating human reason and scientific thought as the instruments of progress and subjecting conventional ways of thinking to rigorous critique.
The Enlightenment culminated with the writings of Jean-Jacques Rousseau (1712-1778) and the Encyclopédistes, the philosophy of Immanuel Kant (1724-1804), and the political ideals of the French and American Revolutions, while the precursor in science and philosophy included Francis Bacon (1561-1626), René Descartes (1596-1650), Isaac Newton (1643-1727), John Locke (1632-1704), and Thomas Hobbes (1588-1679).

Etymology (EN): From enlighten, from en- + → light + -en

• → -ment.

Etymology (PE): Asr, → age; rowšangari, noun from rowšangar “enlightener,” from rowšan “light, bright, luminous, splendid,” cognate with L. lux, → bright, + -gar a suffix of agent nouns, → -or.

To increase the → concentration or → abundance of a specified → component or → isotope in a material.

Etymology (EN): From en- a prefix forming verbs with a particular sense + → rich.

Etymology (PE): Pordâridan, pordâr kardan, infinitives from pordâr, → rich.

To increase the → concentration or → abundance of a specified → component or → isotope in a material.

Etymology (EN): From en- a prefix forming verbs with a particular sense + → rich.

Etymology (PE): Pordâridan, pordâr kardan, infinitives from pordâr, → rich.

Supplied with abundance of something. → enriched gas, → enriched uranium.

See also: Past participle of → enrich.

Supplied with abundance of something. → enriched gas, → enriched uranium.

See also: Past participle of → enrich.

A gas, usually → interstellar, in which the → abundance of particular chemical or atomic species is higher than the expected values.

See also: → enriched; → gas.

A gas, usually → interstellar, in which the → abundance of particular chemical or atomic species is higher than the expected values.

See also: → enriched; → gas.

Uranium in which the → proportion of the → isotope U-235 has been increased (above the 0.7% value in natural uranium).

See also: → enriched; → uranium.

Uranium in which the → proportion of the → isotope U-235 has been increased (above the 0.7% value in natural uranium).

See also: → enriched; → uranium.

1. A process that changes the → isotopic ratio in a material. For example, for uranium the ratio of U-235 to U-238 may be increased by gaseous diffusion of uranium hexafluoride.
   

2. → chemical enrichment.

See also: Verbal noun of → enrich.

1. A process that changes the → isotopic ratio in a material. For example, for uranium the ratio of U-235 to U-238 may be increased by gaseous diffusion of uranium hexafluoride.
   

2. → chemical enrichment.

See also: Verbal noun of → enrich.

A relatively common mineral, magnesium silicate (MgSiO₃) found in metamorphic and some igneous rocks as well as in stony and iron meteorites.

See also: From Gk. enstates “resistor”, because it resists high temperatures.

A relatively common mineral, magnesium silicate (MgSiO₃) found in metamorphic and some igneous rocks as well as in stony and iron meteorites.

See also: From Gk. enstates “resistor”, because it resists high temperatures.

A rare kind of → meteorite containing the → enstatite mineral. These meteorites are thought to comprise only about 2% of the chondrites that fall on Earth. Also called → E-type chondrite.

See also: → enstatite; → chondrite.

A rare kind of → meteorite containing the → enstatite mineral. These meteorites are thought to comprise only about 2% of the chondrites that fall on Earth. Also called → E-type chondrite.

See also: → enstatite; → chondrite.

To wrap or twist together; to intertwine.

Etymology (EN): From → en- “in,” + tangle, from M.E. tangilen, tagilen “to entangle.”

Etymology (PE): Hamgureš, from ham- “together,” → com-,

• guridan “to become tangled, as threads or hairs, entwine,” probably related to greh “knot,” → node.
  Hampicidan, from ham- + picidan “to twist, entwine, coil.”

To wrap or twist together; to intertwine.

Etymology (EN): From → en- “in,” + tangle, from M.E. tangilen, tagilen “to entangle.”

Etymology (PE): Hamgureš, from ham- “together,” → com-,

• guridan “to become tangled, as threads or hairs, entwine,” probably related to greh “knot,” → node.
  Hampicidan, from ham- + picidan “to twist, entwine, coil.”

The act of entangling. The state of being entangled.

See also: Verbal noun of → entangle; → -ment.

The act of entangling. The state of being entangled.

See also: Verbal noun of → entangle; → -ment.

1. To come or go in.
   

2. To put in or insert. See also → entrance, → entry.

Etymology (EN): M.E. entren, from O.Fr. entrer, from L. intrare “to enter,” from intra “within,” → inter-.

Etymology (PE): Darâmadan, from dar, → in-, + âmadan, “to come,” → egress; darâyidan, from dar- “in,” + ây preset stem of âmadan, → assembly, + -idan infinitive suffix; darâyândan transitive of darâyidan.

1. To come or go in.
   

2. To put in or insert. See also → entrance, → entry.

Etymology (EN): M.E. entren, from O.Fr. entrer, from L. intrare “to enter,” from intra “within,” → inter-.

Etymology (PE): Darâmadan, from dar, → in-, + âmadan, “to come,” → egress; darâyidan, from dar- “in,” + ây preset stem of âmadan, → assembly, + -idan infinitive suffix; darâyândan transitive of darâyidan.

A quantity associated with a thermodynamic system and given by H = U + pV, where H is the enthalpy, U the internal energy, p the pressure, and V the volume.

Etymology (EN): Gk. enthalp(ein) “to warm in,” from en- “in, into, within” + thalpein “to warm” + -y a suffix used in the formation of action nouns from verbs.

Etymology (PE): Darungarmi, from darun “in, into, within” (Mid.Pers. andarôn “inside,” from andar, → inter- + rôn “side, direction;” Av. ravan- “(course of a) river”) + garm “warm” (Mid.Pers. garm; O.Pers./Av. garema- “hot, warm;” cf. Skt. gharmah “heat;” Gk. thermos “warm;” L. formus “warm,” fornax “oven;” P.Gmc. *warmaz; O.E. wearm; O.H.G., Ger. warm; from PIE base *ghworm-/*ghwerm-)

• -i a suffix used in the formation of action nouns from verbs.

A quantity associated with a thermodynamic system and given by H = U + pV, where H is the enthalpy, U the internal energy, p the pressure, and V the volume.

Etymology (EN): Gk. enthalp(ein) “to warm in,” from en- “in, into, within” + thalpein “to warm” + -y a suffix used in the formation of action nouns from verbs.

Etymology (PE): Darungarmi, from darun “in, into, within” (Mid.Pers. andarôn “inside,” from andar, → inter- + rôn “side, direction;” Av. ravan- “(course of a) river”) + garm “warm” (Mid.Pers. garm; O.Pers./Av. garema- “hot, warm;” cf. Skt. gharmah “heat;” Gk. thermos “warm;” L. formus “warm,” fornax “oven;” P.Gmc. *warmaz; O.E. wearm; O.H.G., Ger. warm; from PIE base *ghworm-/*ghwerm-)

• -i a suffix used in the formation of action nouns from verbs.

To give a particular title to.

See also: From en-, → in-, + → title.

To give a particular title to.

See also: From en-, → in-, + → title.

Having the title.

See also: Past participle of → entitle.

Having the title.

See also: Past participle of → entitle.

1. A real thing.
   

2. Being or existence, especially when considered as independent, separate, or self-contained.
   

3. Computer science: Something about which data is recorded. Entities have → attributes.

Etymology (EN): From L.L. entitatem, from L.L. ens (genitive entis) “being, thing,” from esse “to be,” cognate with Pers. hast, ast, as below.

Etymology (PE): Hastâr, from hast (noun), as in hast-o-nist, or contraction of hasti “existence,” from hastan “to be” (variant astan, ast “is;” Mid.Pers. (h)ast “is,” (h)astih “existence;” O.Pers. ah- “to be,” astiy “is;”
Av. ah- “to be” (ahmī, ahī, astī); cf. Skt. as- “to be,” ásti “is;” Gk. esti “is;” L. est “is;” Russ. yest “is;” Goth. ist; E. is), + suffix -âr (as in padidâr). Alternatively, from hast (noun), as above, + -âr contraction of -dâr (as in dustâr) present stem of dâštan “to have, to possess” (Mid.Pers. dâštan, O.Pers./Av. root dar- “to hold, keep back, maintain, keep in mind,” Skt. dhr-, dharma- “law,”
Gk. thronos “elevated seat, throne,” L. firmus “firm, stable,” Lith. daryti “to make,” PIE *dher- “to hold, support”).

1. A real thing.
   

2. Being or existence, especially when considered as independent, separate, or self-contained.
   

3. Computer science: Something about which data is recorded. Entities have → attributes.

Etymology (EN): From L.L. entitatem, from L.L. ens (genitive entis) “being, thing,” from esse “to be,” cognate with Pers. hast, ast, as below.

Etymology (PE): Hastâr, from hast (noun), as in hast-o-nist, or contraction of hasti “existence,” from hastan “to be” (variant astan, ast “is;” Mid.Pers. (h)ast “is,” (h)astih “existence;” O.Pers. ah- “to be,” astiy “is;”
Av. ah- “to be” (ahmī, ahī, astī); cf. Skt. as- “to be,” ásti “is;” Gk. esti “is;” L. est “is;” Russ. yest “is;” Goth. ist; E. is), + suffix -âr (as in padidâr). Alternatively, from hast (noun), as above, + -âr contraction of -dâr (as in dustâr) present stem of dâštan “to have, to possess” (Mid.Pers. dâštan, O.Pers./Av. root dar- “to hold, keep back, maintain, keep in mind,” Skt. dhr-, dharma- “law,”
Gk. thronos “elevated seat, throne,” L. firmus “firm, stable,” Lith. daryti “to make,” PIE *dher- “to hold, support”).

1. An act of entering, as into a place or upon new duties.
   

2. A point or place of entering; an opening or passage for entering, as a doorway (Dictionary.com).

→ entrance pupil, → entrance slit.

Etymology (EN): M.E. entraunce, from M.Fr. entrance, from → enter + → -ance.

Etymology (PE): Darâyeš, verbal noun of darâmadan, darâyidan, → enter; darâygâh with space suffix -gâh.

1. An act of entering, as into a place or upon new duties.
   

2. A point or place of entering; an opening or passage for entering, as a doorway (Dictionary.com).

→ entrance pupil, → entrance slit.

Etymology (EN): M.E. entraunce, from M.Fr. entrance, from → enter + → -ance.

Etymology (PE): Darâyeš, verbal noun of darâmadan, darâyidan, → enter; darâygâh with space suffix -gâh.

In an → optical system, the image of the → aperture stop formed in → object space. See also → exit pupil.

See also: → entrance; → pupil.

In an → optical system, the image of the → aperture stop formed in → object space. See also → exit pupil.

See also: → entrance; → pupil.

A thin slit in an opaque screen by which light enters a spectrograph.

See also: → entrance; → slit.

A thin slit in an opaque screen by which light enters a spectrograph.

See also: → entrance; → slit.

1. A measure of the energy that is not available for work during a → thermodynamic process. It is defined by dS = dQ/T, where dS is the differential change in entropy, dQ is the differential amount of heat introduced to the system in a → reversible process, and T the → absolute temperature of the system. Entropy remains constant during → reversible processes and increases during → irreversible processes without ever decreasing. According to the → second law of thermodynamics, an → isolated system evolves toward a state of maximum entropy. See also → Maxwell’s demon.
   

2. Statistical physics: A measure of → disorder of the configuration of → microstates which make up a → macrostate.
   → Boltzmann’s relation, → Boltzmann’s entropy formula. Highly disordered systems have a large entropy; highly ordered systems have low entropy.
   

3. Math.: A measure of information content. → information entropy.

Etymology (EN): From Ger. Entropie, coined 1865 by physicist Rudolf Clausius (1822-1888) from Gk. entropia “a turning toward,” from en- “in” + trope “a turning, change,” related to tropos “a turn, way, manner,” from tropein “to turn,” from PIE base *trep- “to turn” (cf. L. trepit “he turns”).

Etymology (PE): Dargâšt, from dar “in” + gâšt present stem of gâštan “to cause to revolve, to turn,” transitive of gaštan, variant gardidan “to turn, to change” (Mid.Pers. vartitan; Av. varət- “to turn, revolve;” cf. Skt. vartati; L. vertere; O.H.G. werden “to become;”
PIE base *wer- “to turn, bend”).

1. A measure of the energy that is not available for work during a → thermodynamic process. It is defined by dS = dQ/T, where dS is the differential change in entropy, dQ is the differential amount of heat introduced to the system in a → reversible process, and T the → absolute temperature of the system. Entropy remains constant during → reversible processes and increases during → irreversible processes without ever decreasing. According to the → second law of thermodynamics, an → isolated system evolves toward a state of maximum entropy. See also → Maxwell’s demon.
   

2. Statistical physics: A measure of → disorder of the configuration of → microstates which make up a → macrostate.
   → Boltzmann’s relation, → Boltzmann’s entropy formula. Highly disordered systems have a large entropy; highly ordered systems have low entropy.
   

3. Math.: A measure of information content. → information entropy.

Etymology (EN): From Ger. Entropie, coined 1865 by physicist Rudolf Clausius (1822-1888) from Gk. entropia “a turning toward,” from en- “in” + trope “a turning, change,” related to tropos “a turn, way, manner,” from tropein “to turn,” from PIE base *trep- “to turn” (cf. L. trepit “he turns”).

Etymology (PE): Dargâšt, from dar “in” + gâšt present stem of gâštan “to cause to revolve, to turn,” transitive of gaštan, variant gardidan “to turn, to change” (Mid.Pers. vartitan; Av. varət- “to turn, revolve;” cf. Skt. vartati; L. vertere; O.H.G. werden “to become;”
PIE base *wer- “to turn, bend”).

1. An act of entering; → entrance.
   

2. Permission or right to enter; access.
   

3. A place of ingress or entrance, especially an entrance hall or vestibule.
   

4. The act of entering or recording something in a book, register, list, etc. The statement, item, etc., so entered or recorded (Dictionary.com).

Etymology (EN): M.E. entre(e), from O.Fr. entree, from L. intrata, p.p. of intrare “to → enter.”

Etymology (PE): Darâyé, noun from darây present stem of darâmadan, darâyidan, → enter, + -é noun suffix.

1. An act of entering; → entrance.
   

2. Permission or right to enter; access.
   

3. A place of ingress or entrance, especially an entrance hall or vestibule.
   

4. The act of entering or recording something in a book, register, list, etc. The statement, item, etc., so entered or recorded (Dictionary.com).

Etymology (EN): M.E. entre(e), from O.Fr. entree, from L. intrata, p.p. of intrare “to → enter.”

Etymology (PE): Darâyé, noun from darây present stem of darâmadan, darâyidan, → enter, + -é noun suffix.

A shell of dust or gas expanding out from an astronomical object such as a star or a comet’s nucleus.

Etymology (EN): From Fr. enveloppe, from O.Fr. envoloper “to envelop,” from en- “in” + voloper “wrap up,” of obscure origin, perhaps related to M.L. aluppa “a very thin piece or slice of wood” and influenced by L. volvere “to roll.”

Etymology (PE): Pušé, noun from pušidan “to cover; to put on;” Mid.Pers. pôšidan, pôš- “to cover; to wear;” cf. Mid.Pers. pôst; Mod.Pers. pust “skin, hide;” O.Pers. pavastā- “thin clay envelope used to protect unbaked clay tablets;” Skt. pavásta- “cover,” Proto-Indo-Iranian *pauastā- “cloth.”

A shell of dust or gas expanding out from an astronomical object such as a star or a comet’s nucleus.

Etymology (EN): From Fr. enveloppe, from O.Fr. envoloper “to envelop,” from en- “in” + voloper “wrap up,” of obscure origin, perhaps related to M.L. aluppa “a very thin piece or slice of wood” and influenced by L. volvere “to roll.”

Etymology (PE): Pušé, noun from pušidan “to cover; to put on;” Mid.Pers. pôšidan, pôš- “to cover; to wear;” cf. Mid.Pers. pôst; Mod.Pers. pust “skin, hide;” O.Pers. pavastā- “thin clay envelope used to protect unbaked clay tablets;” Skt. pavásta- “cover,” Proto-Indo-Iranian *pauastā- “cloth.”

1. An aggregate of surrounding → circumstances, → conditions, or → influences
   in which a thing is situated or is developed.
   

2. Computers: The entire set of conditions under which one operates a → computer, as it relates to the hardware, operating platform, or operating system.
   

3. Ecology: The totality of circumstances surrounding an → organism or group of organisms. More specifically, the combination of external physical conditions that affect and influence the growth, development, and survival of organisms.

Etymology (EN): From environ + -ment; the first component from Fr. environs, plural of O.Fr. environ “compass, circuit,” from environ (adv.) “around,” from en- “in” + viron “circle, circuit,” from virer “to turn.”

Etymology (PE): Pargir, from par- “around, surrounding,” variant pirâ-→ circum- + gir agent noun and present stem of gereftan “to take, seize; to make prisoner; to intercept” (Mid.Pers. griftan; Av./O.Pers. grab- “to take, seize;” cf.
Skt. grah-, grabh- “to seize, take,” graha “seizing, holding, perceiving;” M.L.G. grabben “to grab,” from P.Gmc. *grab; E. grab “to take or grasp suddenly;” PIE base *ghrebh- “to seize”).
Zistbum, from zist “life, existence,” → bio-,

• bum “region, land, place,” → eco-.

1. An aggregate of surrounding → circumstances, → conditions, or → influences
   in which a thing is situated or is developed.
   

2. Computers: The entire set of conditions under which one operates a → computer, as it relates to the hardware, operating platform, or operating system.
   

3. Ecology: The totality of circumstances surrounding an → organism or group of organisms. More specifically, the combination of external physical conditions that affect and influence the growth, development, and survival of organisms.

Etymology (EN): From environ + -ment; the first component from Fr. environs, plural of O.Fr. environ “compass, circuit,” from environ (adv.) “around,” from en- “in” + viron “circle, circuit,” from virer “to turn.”

Etymology (PE): Pargir, from par- “around, surrounding,” variant pirâ-→ circum- + gir agent noun and present stem of gereftan “to take, seize; to make prisoner; to intercept” (Mid.Pers. griftan; Av./O.Pers. grab- “to take, seize;” cf.
Skt. grah-, grabh- “to seize, take,” graha “seizing, holding, perceiving;” M.L.G. grabben “to grab,” from P.Gmc. *grab; E. grab “to take or grasp suddenly;” PIE base *ghrebh- “to seize”).
Zistbum, from zist “life, existence,” → bio-,

• bum “region, land, place,” → eco-.