An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

1) A small hole such as a space especially in a rock, soil, etc. → porous dust grain, → porosity.
2) A minute orifice in an animal or plant, as in the skin or a leaf.
3) Sun: A small → sunspot that does not have a → penumbra. Pores are up to about 2,500 km across and are lighter than a sunspot's → umbra. They appear and disappear at the surface of the Sun where sunspots are rarely formed, e.g. at low latitudes. Their lifetimes can be as short as 1/2 hour and as long as several days.

From L. porus "a pore," from Gk. poros "a pore," literally "passage, way," from PIE root *per- "to lead, pass over."

Lik, from Gilaki lik "hole," variants luk, luke, liuk, luxa, Tabari luk, li, Sangesari, Semnâni lu, Aftari lo.

1) General: A → dimensionless number characterizing a porous medium, expressed by the ratio of the volume occupied by the pores to the total volume of the medium.
2) Geology: The percentage volume of hollow spaces in a rock, sediment, or soil.
3) Dust grains: The quantity usually defined as: P = (V_v/V_t) = (1 - V_s/V_t), where V_v and V_s are the volumes of vacuum and of the solid matter making up the particle, and V_t is the total volume of the particle within some defined surface.

→ porous; → -ity.

Full of pores.

From M.Fr. poreux, from M.L. porosus, from L. porus "opening," → pore.

Porlik, from por "full; many," → full, + lik, → pore.

A type of → interstellar dust grain made up of an aggregate of components with a hollow structure. Various processes operating in interstellar and → circumstellar media are believed to produce inhomogeneous and porous dust grains. Porous grains can produce more → extinction per unit mass than their combined individual dust components. They are generally cooler than compact grains (see, e.g., Iati et al. 2001, MNRAS 322, 749).

→ porous; → dust; → grain.

A → binary star in the constellation → Virgo comprising two yellow-white → main sequence stars of +3.6 and +3.7 magnitude and spectral types F0V. Their orbital period is about 170 years and they are about 40 light-years away.

Porrima after the Roman goddess of childbirth.

A World Wide Web site that functions as an entry point to the Internet and is accessed through a browser.

M.E. portale "city gate, porch," from M. L. portalis (adj.) "of a gate," from L. porta "gate, door."

Dargâh, from Mid.Pers. dargâh "doorway," from dar "door" (O.Pers. duvara-; Av. dvar-; cf. Skt. dvár-; Gk. thura, L. fores; O.E. duru; E. door; Lith. dvaras "court-yard;" PIE *dhwer-/*dhwor- "door, gate") + gâh "place; time" (Mid.Pers. gâh, gâs; O.Pers. gāθu-; Av. gātav-, gātu- "place, throne, spot;" cf. Skt. gátu- "going, motion; free space for moving; place of abode;" PIE *gwem- "to go, come").

1) A part of any whole, either separated from or integrated with it.
2) To divide into or distribute in portions or shares.

M.E. porcion, from O.Fr. porcion "part, portion, share," from partion- "share, part, piece," related to pars, → part.

Pâreš, from pâr "part, portion, piece" (variants pâré, parré "portion, segment (of an orange)," pargâlé, "piece, portion; patch;" (dialects Kermâni pariké "portion, half;" Tabari perik "minute quantity, particle;" Lârestâni pakva "patch;" Borujerdi parru "patch"); Mid.Pers. pârag "piece, part, portion; gift, offering, bribe;" Av. pāra- "debt," from par- "to remunerate, equalize; to condemn;" PIE *per- "to sell, hand over, distribute; to assigne;" Gk. peprotai "it has been granted;" L. pars, as above; Skt. purti- "reward;" Hitt. pars-, parsiya- "to break, crumble") + -eš suffix.

1a) Condition with reference to place; location; situation.
1b) A place occupied or to be occupied. → mean position.
2a) To put in a particular or appropriate position; place.
2b) To determine the position of; locate.

M.E. posicioun, from O.Fr. posicion, from L. positionem "act or fact of placing, position, affirmation," from positus, p.p. stem of ponere "to put, place."

Neheš, verbal noun from nehâdan "to place, put; to set;" Mid.Pers. nihâtan, from ne-, ni- "down; into," → ni- (PIE), + dâ- "to put; to establish; to give," dadâiti "he gives;" cf. Skt. dadâti "he gives;" Gk. didomi "I give;" L. do "I give;" PIE base *do- "to give"). Neheš-dâdan, from neheš "position," + dâdan "to give, yield, put," → datum.

The convention for measuring angles on the sky in astronomy (Abbreviated as PA). It is the direction of an imaginary arrow in the sky, measured from north through east: 0° = north, 90° = east, 180° = south, and so on to 359° and back to 0°. Applied to a binary system it is the direction of a secondary body or feature from a primary, measured in the system. .

→ position; → angle.

In single dish astronomy, an observing mode in which the telescope is moved between the object position and a user defined reference position. The aim is to eliminate unwanted signals in the baseline. → beam switching; → frequency switching.

→ position; → switching.

Relating to or determined by position.

→ position; → -al.

The branch of astronomy that is used to determine the location of objects on the celestial sphere, as seen at a particular date, time, and location on the Earth. Same as → spherical astronomy.

→ positional; → astronomy.

A system of representing → numbers in which the → position of a → digit in a string of digits affects its value. The decimal system is a positional notation for expressing numbers. Same as → place-value notation and → positional number system.

→ positional; → notation.

A → number system in which the value of each digit is determined by which place it appears in the full number. The lowest place value is the rightmost position, and each successive position to the left has a higher place value. In the → number system conversion, the rightmost position represents the "ones" column, the next position represents the "tens" column, the next position represents "hundreds", etc. The values of each position correspond to powers of the → base of the number system. For example, in the usual decimal number system, which uses base 10, the place values correspond to powers of 10. Same as → place-value notation and → positional notation. See also → number system conversion.

→ positional; → number; → system.

The act or process of putting in a particular position or determining the psition of.

Verbal noun of → position; → -ing.

1) General: Explicitly stated, stipulated, or expressed.
2) Capable of being measured, detected, or perceived.
3) Math.: Noting a quantity greater than zero.
4) Physics: Having an electrical charge of the same polarity as that of a proton.
5) Photography: Having colors or values of dark and light corresponding to the subject.
6) Philosophy: Relating to the theory that knowledge can be acquired only through direct observation and experimentation, and not through metaphysics or theology. → positivism.
7) Law: Conclusive and beyond doubt or question; irrefutable.
8) Opposite of → negative.
See also:
→ positive charge, → positive correlation, → positive feedback, → positive skewness, → positiveness, → positivism.

M.E., from O.Fr. positif, from L. positivus "placed, settled; positive" (opposed to naturalis "natural"), from posit-, from positus "placed, put," p.p. of ponere "to put, place, set" + -ivus a suffix of adjectives.

Dâhidâr, from dâhid- + -âr. The first component is the past stem of *dâhidan "to put, create, determine," variant of dehidan, dâdan "to give;" from Mid.Pers. dâdan, dahidan "to give; to create;" O.Pers. dā- "to give, grant, yield;" Av. dā- "to give, grant; put; create; determine;" dāhi "he would give/put" (single second person, subjunctive transitive), dadāiti "he gives;" cf. Skt. dadáti "he gives;" Gk. tithenai "to place, put, set," didomi "I give;" L. dare "to give, offer," facere "to do, to make;" Rus. delat' "to do;" O.H.G. tuon, Ger. tun, O.E. don "to do;" PIE base *dhe- "to put, to do." The second component -âr, accusative suffix; on the model of gereftâr "captive, involved (in trouble)," didâr "exposed to view."

A charge having sign opposite to that of the electron.

→ positive; → charge.

Same as → direct correlation.

→ positive; → correlation.

A → feedback process in which the → output reacts on the → input so as to increase the initial → effect.

→ positive; → feedback.

Of a distribution function, a skewness in which the right tail (tail at the large end of the distribution) is more pronounced than the left tail (tail at small end of the distribution). → negative skewness.

→ positive; → skewness.