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

A → stellar wind in which the gas is subject to only two forces: the inward directed gravity and the outward directed gradient of the gas pressure.

→ isothermal; → wind.

One of several nuclides having the same number of neutrons in their nuclei but differing in the number of protons.

Isotone, from → iso- + tone, from Gk tonos "strain, tone, mode," literally, "a stretching," akin to teinein "to stretch," cognate with Pers. tanidan "to spin, twist, weave" (Mid.Pers. tanitan; Av. tan- "to stretch, extend;" cf. Skt. tan- to spin, stretch;" tanoti "stretches," tantram "loom;" Gk. teinein "to stretch, pull tight;" L. tendere "to stretch; PIE base *ten- "to stretch;" Pers. târ "string," tân "thread," tur "fishing net, net, snare," and tâl "thread" (Borujerdi dialect) belong to this family; variants tanta "cobweb," tanadu, tafen, kartané, kârtané, kâtené, Pashtu tanistah "cobweb;" cf. Skt. tantu- "cobweb, thread, string").

One of two or more atoms having the same number of protons in its nucleus, but a different number of neutrons and, therefore, a different mass.

Isotope, from → iso- + -tope, from Gk. topos "place."

Izotop, loan from Fr., as above. hamjâ, from ham- "together" → com- + jâ "place" (from Mid.Pers. giyag "place;" O.Pers. ā-vahana- "place, village;" Av. vah- "to dwell, stay," vanhaiti "he dwells, stays;" Skt. vásati "he dwells;" Gk. aesa (nukta) "to pass (the night);" Ossetic wat "room; bed; place;" Tokharian B wäs- "to stay, wait;" PIE base ues- "to stay, live, spend the night").

A slight difference between the → abundances of → isotopes of the same → chemical element owing to → physical or → chemical  → processes. It results in the → enrichment or → depletion of an isotope. Same as → isotopic fractionation.

→ isotope; → fractionation

A displacement in the spectral lines due to the different isotopes of an element.

→ isotope; → shift.

Of or relating to an → isotope.

→ isotope; → -ic.

Same as → isotope fractionation.

→ isotopic; → fractionation

The difference between the number of neutrons in an isotope and the number of protons. Neutron excess.

→ isotopic; → number.

The relative abundances of two isotopes of a given chemical element, such as D/H (deuterium/hydrogen), (carbon) ¹²C/¹³C, and (uranium) ²³⁵U/²³⁸U.

→ isotopic; → ratio.

Same as → isospin.

→ isotopic; → spin.

Any of molecular entities which differ in their isotopic composition but retain the same → chemical elements, e.g. H₂O and HDO.

Abbreviation of → isotopic → analogue.

Any of → isomers having the same number of each isotopic atom but differing in their positions. For example, CH₃CHDCH₃ and CH₃CH₂CH₂D are a pair of isotopomers.

Short for isotopic isomers.

Having physical properties that do not vary with direction.

→ iso- + → -tropic.

A Universe having observed properties that appear identical in every direction.

→ isotropic; → universe.

The property by which physical properties are equal along all directions. → anisotropy.

Isotropy, noun of → isotropic.

1a) A result or outcome of something.
1b) The action of flowing or coming out.
1c) Each of a regular series of publications.
1d) An important topic or problem for debate or discussion.
2) Formally send out or make known (OxfordDictionaries.com).

M.E., from O.Fr. issue "a way out, a going out, exit; final event," from L. exire "to go out, go forth; become public; flow, pour forth," from → ex- "out," + ire "to go,"

Borunây, literally "what comes out, exits," from borun, → out, + ây- present stem of âmadan "to come, arrive, become," → precession.

1) A distinct part in an enumeration, account, collection, or set.
2) An object of attention, concern, or interest.
3) A separate piece of news or information.

From M.E. item, from L. item ("also; in the same manner"), from a L. usage in lists, where the first entry would begin in primis ("firstly") and the other entries with item ("also, moreover").

Yutar, from Sogd. yûtar "one of several," from ēw-tar, from ēw "→ one" + -tar distinction suffix.

1) To present as a list of items.
2) To list the items of.

→ item; → -ize.

1) To utter or to do something over again or repeatedly. → repeat.
2) Math.: → iteration.

Iterate "to do again, repeat," back-formation from iteration, from L. iterationem (nom. iteratio) "repetition," noun of action from iterare "to do again, repeat," from iterum "again, for the second time;" cf. Skt. itara- "the other (of the two), another."

Itaridan, from L. iter(um), Skt. itar(a-), as above, and Pers. dialects Kâšâni (Voništun) târ "the other;" Kurd. tir "the other" + -idan Pers. infinitive suffix.

A computational process involving a succession of approximations, which consists of repeating the operation by inputting the outcome of each preceding operation to improve the final result until a desired accuracy is achieved. Compare → repetition.

Verbal noun of → iterate.