sēmi- — Lewis & Short
sēmi- (also, before vowels, merely sēm-, and before libra, mestris, from mensis, and modius, sē-), an inseparable particle [Sanscr. sāmi; Gr. h(mi-, h(/misus; cf. semis],
I half, demi-, semi-; as, semestris, semi-monthly; semesus, half-eaten; semideus, demigod, etc.; hence, also, for small, thin, light, etc.; as, semicinctium, semifunium, semipiscina, semispatha, al.—Only a very few of these compounds are ante-Aug.; most of them, indeed, belong only to the post-class. per.