VARIABLE NOUNS
[*] 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 -us, vary between the Second and Fourth Declensions.
[*] b. Some nouns vary between the Second and Third: as, iūgerum , -ī, -ō, ablative -ō or -e, plural -a, -um, -ibus; Mulciber, genitive -berī and -beris; sequester, genitive -trī and -tris; vās , vāsis , and (old) vāsum , -ī (§ 79. e).
[*] c. Some vary between the Second, Third, and Fourth: as, penus , penum , genitive penī and penoris , ablative penū.
[*] d. Many nouns vary between the First and Fifth (see § 98. c).
[*] e. Some vary between the Third and Fifth. Thus, requiēs has genitive -ētis, dative wanting, accusative -ētem or -em, ablative -ē (once -ēte); famēs, regularly of the third declension, has ablative famē (§ 76. N. 1), and pūbēs (M.) has once dative pūbē (in Plautus).
[*] f. Pecus varies between the Third and Fourth, having pecoris , etc., but also nominative pecū , ablative pecū; plural pecua, genitive pecuum .
[*] g. Many vary between different stems of the same declension: as, femur (N.), genitive -oris, also -inis (as from † femen ); iecur (N.), genitive 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:—
[*] Note.--Some of these nouns are heteroclites as well as heterogeneous.
| balneum (N.), bath; | balneae (F.), baths (an establishment). |
| caelum (N.), heaven; | caelōs (M. acc., Lucr.). |
| carbasus (F.), a sail; | carbasa (N.) (-ōrum), 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. |
[*] 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 (town-meeting). |
| 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 gardon; | hortī, pleasure-grounds. |
| impedīmentum (N.) hindrance; | impedīmenta, baggage. |
| littera (F.), letter (of alphabet); | litterae, epistle, literature. |
| locus (M.), place [plural loca (N.)]; | locī,3 topics, places in books. |
| lūdus (M.), 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. or N.), salt; | salēs, witticisms. |
| tabella (F.), tablet; | tabellae, documents, records. |