58. Most mute stems are masculine or feminine. Those that are neuter have for the nominative the simple stem. But—
a. Lingual Stems (t, d) ending in two consonants drop the final mute.
cor (stem cord-)
lac (stem lact-)
So also stems in ăt- from the Greek.
poēma (stem poēmat-)
b. The stem capit- shows u in the nominative (caput for †capot).
59. Nouns of this class are declined as follows.
60. The following irregularities require notice.
a. Greek neuters with nominative singular in -a (as poēma) frequently end in -īs in the dative and ablative plural, and rarely in
-ōrum in the genitive plural.
poēmatīs (for poēmatibus), poēmatōrum (for poēmatum)
b. A number of monosyllabic nouns with mute stems lack the genitive plural (like cor). See § 103.g.2.