hebdomas, adis, f., = ἑβδομάς, the number seven, seven days: libri, qui inscribuntur Hebdomades, Gell. 3, 10, 1: septima fere hebdomade, id est, nono et quadragesimo die, Varr. ib. § 7: hebdomadibus lunae, on every seventh day of the moon, Gell. 15, 2, 3.

—Of the critical seventh day in diseases: symphoniam Lysonis vellem vitasses, ne in quartam hebdomada incideres, Cic. Fam. 16, 9, 3 (cf. collat. form hebdomada, s. v.).