dies res res
_Abl._ die diebus re rebus

Peculiarities of Nouns of the Fifth Declension.

52. 1. The ending of the Genitive and Dative Singular is -ei, instead of
-ei, when a consonant precedes; as, spei, rei, fidei.

2. A Genitive ending -i (for -ei) is found in plebi (from plebes = plebs)
in the expressions tribunus plebi, _tribune of the people_, and plebi
scitum, _decree of the people_; sometimes also in other words.

3. A Genitive and Dative form in -e sometimes occurs; as, acie.

4. With the exception of dies and res, most nouns of the Fifth Declension
are not declined in the Plural. But acies, series, species, spes, and a few
others are used in the Nominative and Accusative Plural.

Gender in the Fifth Declension.

53. Nouns of the Fifth Declension are regularly Feminine, except dies,
_day_, and meridies, _mid-day_. But dies is sometimes Feminine in the
Singular, particularly when it means an _appointed day_.

* * * * *

DEFECTIVE NOUNS.

54. Here belong--

1. Nouns used in the Singular only.

2. Nouns used in the Plural only.

3. Nouns used only in certain cases.

4. Indeclinable Nouns.

Nouns used in the Singular only.

55. Many nouns, from the nature of their signification, are regularly used
in the Singular only. Thus:--

1. Proper names; as, Cicero, _Cicero_; Italia, _Italy_.

2. Nouns denoting material; as, aes, _copper_; lac, _milk_.

3. Abstract nouns; as, ignorantia, _ignorance_; bonitas, _goodness_.

4. But the above classes of words are sometimes used in the Plural. Thus:--

a) Proper names,--to denote different members of a family, or specimens
of a type; as, Cicerones, _the Ciceros_; Catones, _men like Cato_.

b) Names of materials,--to denote objects made of the material, or
different kinds of the substance; as, aera, _bronzes_ (i.e. bronze
figures); ligna, _woods_.

c) Abstract nouns,--to denote instances of the quality; as, ignorantiae,
_cases of ignorance_.

Nouns used in the Plural only.

56. Here belong--

1. Many geographical names; as, Thebae, _Thebes_; Leuctra, _Leuctra_;
Pompeji, _Pompeii_.

2. Many names of festivals; as, Megalesia, _the Megalesian festival_.

3. Many special words, of which the following are the most important:--

angustiae, _narrow pass_. manes, _spirits of the
arma, _weapons_. dead_.
deliciae, _d