edited by Meagan Ayer et al.

Variable Nouns

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104. Many nouns vary either in Declension or in Gender.

105. Nouns that vary in Declension are called heteroclites.1

a. Colus (f.), distaff; domus (f.), house (see § 93), and many names of plants in -u, vary between the 2nd and 4th Declensions.

b. Some nouns vary between the 2nd and 3rd:

iūgerum, , , abl. or -e, plural -a, -um, -ibus
Mulciber, gen. -berī and -beris
sequester, gen. -trī and -tris
vās, vāsis, and (old) vāsum, (§ 79.e).

c. Some vary between the 2nd, 3rd, and 4th.

penus, penum, gen. penī and penoris, abl. penū.

d. Many nouns vary between the 1st and 5th (see § 98.c).

e. Some vary between the 3rd and 5th.

requiēs, gen. -ētis, dat. — , acc. -ētem or -em, abl.  (once
famēs, regularly of the 3rd declension, abl. famē (§ 76, Note 1)
pūbēs (m.) has once dat. pūbē (in Plautus).

f. Pecus varies between the 3rd and 4th, having pecoris, etc., but also nom. pecū, abl. pecū; plural pecua, gen. pecuum.

g. Many vary between different stems of the same declension:

femur (n.), gen. -oris, also -inis (as from † femen)
incur (n.), gen. iecinoris, iocinoris, iecoris
mūnus (n.), plural mūnera and mūnia.

106. Nouns that vary in Gender are said to be heterogeneous.2

a. The following have a masculine form in -us and a neuter in -um:

balteus, cāseus, clipeus, collum, cingulum, pīleus, tergum, vāllum

with many others of rare occurrence.

b. The following have in the plural a different gender from that of the singular:

balneum (n.) bath balneae (f.) baths (an establishment)
caelum (n.) heaven caelōs [(m.) acc., Lucretius]
carbasus (f.) a sail carbasa, -ōrum (n.) sails
dēlicium (n.) pleasure dēliciae (f.) pet
epulum (n.) feast epulae (f.) feast
frēnum (n.) a bit frēnī (m.) or frēna (n.) a bridle
iocus (m.) a jest ioca (n.), iocī (m.) jests
locus (m.) place

loca (n.), locī (m.) usually topics,
passages (in books)

rāstrum (n.) a rake rāstrī (m.), rāstra (n.) rakes

Note— Some of these nouns are heteroclites as well as heterogeneous.

107. Many nouns are found in the Plural in a peculiar sense:

aedēs, -is (f.) temple aedēs, -ium house
aqua (f.) water

aquae mineral springs,
a watering-place

auxilium (n.) help auxilia auxiliaries
bonum (n.) a good bona goods, property
carcer (m.) dungeon carcerēs barriers (of race-course)
castrum (n.) fort castra camp
comitium (n.) place of assembly

comitia an election,

cōpia (f.) plenty cōpiae stores, troops
fidēs (f.) harp-string fidēs lyre
fīnis (m.) end fīnēs bounds, territories
fortūna (f.) fortune fortūnae possessions

grātia (f.) favor
(rarely, thanks)

grātiae thanks
(also, the Graces)

hortus (m.) a garden hortī pleasure-grounds
impedīmentum (n.) hindrance impedīmenta baggage
littera (f.) letter (of alphabet) litterae epistle, literature
locus (m.) place [pl. loca (n.)] locī3 topics, places in books
lūdus sport lūdī public games
mōs (m.) habit, custom mōrēs character
nātālis (m.) birthday nātālēs descent, origin
opera (f.) work operae day-laborers (“hands”)
[ops] opis (f.) help (§ 103.f.1) opēs resources, wealth
pars (f.) part partēs part (on the stage), party
rōstrum (n.) beak of a ship rōstra speaker's platform
sāl (m. / n.) salt salēs witticisms
tabella (f.) tablet tabellae documents, records



1. That is, “nouns of different inflections” (ἔτερος another, and κλινω to inflect).
2. That is, “of different genders” (ἕτερος  another, and γένος  gender).
3. In early writers the regular plural.