§56. Mute Stems
Masculine and Feminine Nouns with mute stems form the Nominative by adding s to the stem.
A labial ( p) is retained before s: as, prīncep-s.
A lingual (t, d) is dropped before s: as, mīles (stem mīlit-), cūstōs (stem cūstōd-).
A palatal (c, g) unites with s to form x: as, dux (for † duc-s), rēx (for † rēg-s).
a. In dissyllabic stems the final syllable often shows e in the nominative and i in the stem: as, prīnceps, stem prīncip- (for -cap-).
J. H. Allen and J. B. Greenough, New Latin Grammar (Boston: Ginn, 1903). Text provided under a CC BY-SA license by Perseus Digital Library, http://www.perseus.tufts.edu, with funding from the National Endowment for the Humanities.