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, Cicerō, _Cicero_; Italia, _Italy_.

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

3. Abstract nouns; as, ignōrantia, _ignorance_; bonitās, _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, Cicerōnēs, _the Ciceros_; Catōnēs, _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, ignōrantiae,