99. Some nouns are ordinarily found in the singular only (singulāria tantum). These are—
- Most proper names.
- Names of things not counted, but reckoned in mass.
- Abstract nouns.
100. Many of these nouns, however, are used in the plural in some other sense.
a. The plural of a proper name may be applied to two or more persons, places, or things, and so become strictly common.
duodecim Caesarēs the twelve Cæsars
Galliae the two Gauls (Cis- and Transalpine)
Castores Castor and Pollux
Iovēs images of Jupiter
b. The plural forms of names of things reckoned in mass may denote particular objects.
aera bronze utensils
Alternatively, the plural may denote different kinds of a thing.
āerēs airs (good and bad)
c. The plural of abstract nouns denotes occasions or instances of the quality, or the like.
quaedam excellentiae some cases of superiority
ōtia periods of rest
calōrēs, frīgora times of heat or cold