I. Orig. belonging to the relig. lang., the dictates of religion, divine law; opp. to jus, or human law (rare; cf. “also: aequitas, justitia): jus ac fas omne delere,” Cic. Att. 1, 16, 6; cf.: “festis quaedam exercere diebus Fas et jura sinunt,” Verg. G. 1, 269: “contra fas, contra auspicia, contra omnes divinas atque humanas religiones,” Cic. Verr. 2, 5, 13, § 34.—Personified: “audi Juppiter, audite Fines, audiat Fas,” Liv. 1, 32, 6: “prima deum Fas quae Themis est Graiis,” Aus. Technop. Idyll. 12: “Fas omne mundi,” i. e. the gods, Sen. Here. Fur. 658.—
II. Transf.
A. A court-day, i. q. fastus (ante-class.): “dies qui vocatur sic: QVANDO REX COMITIAVIT, FAS,” Varr. L. L. 6, §§ 31, 32.—
B. In gen. (justice, equity, but usu. to be translated as an adjective), right, proper, allowable, lawful, fit, permitted; hence, possible (the predominant meaning of the word in prose and poetry; “esp. freq. in the phrase fas est, with a subjectclause): fas, justum, pium, aequum subjici possunt honestati,” Quint. 3, 8, 26: “cum fas atque nefas exiguo fine libidinum Discernunt avidi,” Hor. C. 1, 18, 10; Ov. M. 6, 585; cf.: “quippe ubi fas versum atque nefas,” Verg. G. 1, 505; Hor. Epod. 5, 87: “jusque fasque est,” Plaut. Cist. 1, 1, 22: “si jus, si fas est,” Ter. Hec. 3, 3, 27: “sicut fas jusque est,” Liv. 7, 31, 3: “ut eum nihil delectaret, quod aut per naturam fas esset aut per leges liceret,” Cic. Mil. 16, 43; cf.: “quoad fas esset, quoad liceret,” id. Agr. 2, 7, 19; and: “huic legi nec obrogari fas est, neque derogari ex hac aliquid licet,” id. Rep. 3, 22: “si me fas est orare etiam abs te, pater, etc.,” Plaut. Bacch. 4, 9, 102: “quid non adeptus est, quod homini fas esset optare?” Cic. Lael. 3, 11: “si eos hoc nomine appellari fas est,” id. Mur. 37, 80: “non esse fas, Germanos superare, si, etc.,” Caes. B. G. 1, 50 fin.: “neque fas esse existimant, ea litteris mandare,” id. ib. 6, 14, 3: “ad quos (libellos) interim respicere fas sit,” Quint. 10, 7, 31: “velut si aliter facere fas non sit,” id. 2, 13, 1; 8, 3, 36; 10, 2, 9; “12, 7, 1: nec scire fas est omnia,” Hor. C. 4, 4, 22: “fas omne est, Cytherea, meis te fidere regnis,” there is every reason, Verg. A. 5, 800: “si hoc fas est dictu,” Cic. Tusc. 5, 13, 38: “neque id me facere fas existimo,” Plaut. As. 3, 1, 11: “fas habere,” id. Trin. 2, 2, 11; Quint. 3, 8, 13; Tac. A. 14, 30; id. G. 9: “leporem et gallinam et anserem gustare fas non putant,” Caes. B. G. 5, 12, 6; 6, 23 fin.: “fas prohibet, etc.,” Ov. Tr. 2, 205: “contra quam fas erat,” Cic. Clu. 5, 12: “ridetque (deus), si mortalis ultra Fas trepidat,” Hor. C. 3, 29, 32: “fas omne abrumpit,” every right, obligation, Verg. A. 3, 55: “exuere,” Tac. H. 3, 5: “et foedera respicere,” id. ib. 4, 67; cf.: “hostium quoque jus et sacra legationis et fas gentium rupistis,” the law of nations, id. A. 1, 42; “so in Tac. freq. = jus: patriae,” the right, claim of one's native land, id. ib. 2, 10: “armorum,” id. H. 4, 58: “disciplinae,” id. A. 1, 19 al.