An Etymological Dictionary of Astronomy and Astrophysics

1a) Math.: An unproved → assumption taken as basic in a mathematical system, and from which (in combination with other → postulates) the propositions of the system are derived, or in terms of which the propositions are proved. In modern usage, postulate is synonymous with → axiom.

1b) Physics: A fundamental principle. For example, the two postulates of special relativity of Einstein are: 1) The laws of physical phenomena are the same when studied in terms of two → reference frames moving at a constant velocity relative to each other. 2) The → velocity of light in free space is the same for all observers and is independent of the relative velocity of the source of light and the observer. See also → Planck postulate.

2a) General: To ask, demand, or claim. To claim or assume the existence or truth of, especially as a basis for reasoning or arguing.

2b) Math.: To assume as a postulate.

Etymology (EN): From L. postulatum “petition, thing requested,” noun use of neuter of p.p. of postulare “to ask, request, demand,” akin to poscere “to request.”

Etymology (PE): Farâvas (on the model of piš-nahâd “proposition,” and farâ-nemudan “to exhibit, expose”), from farâ-, → pro-, + vas. The second component from Av. vas- “to will, desire, wish, long for,” vasəmi “I wish,” vasna- “will, favor,” ušti- “desire, wish, will,” vasô, vasə “at one’s will;” cf. O.Pers. vasiy “at will, greatly, utterly,” vašna- “will, favor;” Mid.Pers. vasnâd “because, on account of.” This word is extant in several Modern Iranian dialects: Tabari vessen “to wish, desire,” Gilaki vâssan “to wish, desire,” vâsti “desire; for, because, on account of;” Kurd. wistin “to desire, wish,” Lâri avessa “to desire;” Nâyini vas “to like;” colloquial Tehrâni vâsé “for;” Lori, Malâyeri biza “pregnancy craving;”
cognate with Skt. vaś- “to wish, want, desire,” váśa- “wish, desire,” vasēna “for, because;” Gk. ekon “voluntary;” PIE base *uek- “to wish.”