c) Requiēs, requiētis, _rest_, regularly of the Third Declension, takes
an Acc. of the Fifth, requiem, in addition to requiētem.

d) Besides plēbs, plēbis, _common people_, of the Third Declension, we
find plēbēs, plēbĕī (also plēbī, see § 52, 2), of the Fifth.

Heterogeneous Nouns.

60. Heterogeneous nouns vary in Gender. Thus:--

1. Several nouns of the Second Declension have two forms,--one Masc. in
-us, and one Neuter in -um; as, clipeus, clipeum, _shield_; carrus, carrum,
_cart_.

2. Other nouns have one gender in the Singular, another in the Plural;
as,--

SINGULAR. PLURAL.
balneum, n., _bath_; balneae, f., _bath-house_.
epulum, n., _feast_; epulae, f., _feast_.
frēnum, n., _bridle_; frēnī, m.(rarely frēna, n.), _bridle_.
jocus, m., _jest_; joca, n. (also jocī, m.), _jests_.
locus, m., _place_; loca, n., _places_; locī, m., _passages
or topics in an author_.
rāstrum, n., _rake_; rāstrī, m.; rāstra, n., _rakes_.

a. Heterogeneous nouns may at the same time be heteroclites, as in case
of the first two examples above.

Plurals with Change of Meaning.