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

1) Logic: Relating to or involving deductive reasoning from a general principle to the expected facts or effects (dictionary.com).
2) Logic: Known to be true independently of or in advance of experience of the subject matter; requiring no evidence for its validation or support (dictionary.com). → a posteriori.

L., literally "from what comes first," from priori, ablative of prior "former, previous, first," → per-.

Partom "the first," Dehxodâ: fardom; Mid.Pers. fradom, fratom, pratom; O.Pers. fratama-; Av. fratəma- (Skt. prathama- "earliest, initial, first") superlative of fra- "before, forward, forth," cognate with Gk. and L. → pro-.