semestrium

μή μοι θεοὺς καλοῦσα βουλεύου κακῶς· πειθαρχία γάρ ἐστι τῆς εὐπραξίας μήτηρ, γυνὴ Σωτῆρος· ὦδ᾽ ἔχει λόγος → When you invoke the gods, do not be ill-advised. For Obedience is the mother of Success, wife of Salvation—as the saying goes.

Latin > English (Lewis & Short)

sēmestrĭum: ii, n. id.,
I a half month, a fortnight, Col. 11, 2, 6.

sēmestrĭum, ĭī, n. (semi, mensis), demi-mois, quinzaine : Col. Rust. 11, 2, 6.

sēmēstrium, iī, n. (semi u. mensis), ein halber Monat, Colum. 11, 2, 6.

semestrium, ii. n. :: 六月之久。Semestria. plur. 律例書名。