Irregular Nouns

Not all nouns in Latin occur in every form, and some of them don't quite follow all of the rules like they should. Here are the kinds of irregularities that occasionally crop up.

Redundant Nouns

One noun that exists in more than one gender. Usually confined to second declension masculines and neuters.

Some Redundant Nouns
abrotunum, -us aevom (um), -us baculum, -us balteus, -um buxus, -um calamister, -um caseus, -um cavom (um), -us cingulum, -us clipeus, -um collum, -us costum, -um forum, -us	a kind of plant age staff girdle box-wood curling-iron cheese cavity belt shield neck a kind of plant market	gladius, -um intibus, -um iugulum, -us nardum, -us nasus, -um palatum, -us pileus, -um sagum, -us tergum, -us thesaurus, -um uterus, -um vallus, -um	sword succory collar-bone nard nose palate cap cloack back treasure womb palisade

Heteroclytes
- Heteroclytes change their declension in some forms.
- vas, vasis, f. 3rd in the singular, but vasa, vasorum, n. 2nd in the plural.
  iugerum, iugeri, n. 2nd in the singular, but iugera, iugerum, n. 3rd in the plural.

Heterogeneous Nouns

Heterogeneous nouns change their gender. Many are also heteroctyles; redundant nouns are similar.

**Some Heteroclytes**
Singular	Plural
baleneum, bath epulum, feast frenum, bridle iocus, joke/jest locus, place rastrum, rake	balneae, bath-house epulae, feast freni or frena, bridle ioca or ioci, jokes/jests loca, places loci, passages, topics rastri or rastra, rakes

Defective Nouns

Some nouns are used only in the singular: nouns naming abstract concepts or materials.
iustitia, justice; aurum, gold

Some nouns are used only in the plural:

Plural Defective Nouns
altaria, -ium, altar ambages, round-about angustiae, straits antae, doorposts antes, rows (of vines) arma, -orum, arms armamenta, -orum, tackle bellaria, -orum, desert bigae, two-hourse (chariot) quadrigae, four-hourse (chariot) cancelli, lattice casses, toils (snare) caulae, openings cervices, neck (poetic) cibaria, victuals claustrum, lock clitellae, pack-saddle codicilli, a short note compedes, fetters crepundia, -orum, rattle cunae, cradle divitiae, riches dumeta, -orum, thorn-bush epulae, banquet excubiae, watching exsequiae, funeral procession exta, -orum, internal organs exuviae, equipment	facetiae, witticism fasti, calendar facues, gullet, throat feriae, holidays flabra, breezes fores, door fraga, -orum, strawberries grates, thanks hiberna, winter quarters Idus, Ides Kalendae, Kalends Nones, Nones incunabula, swaddling-clothes indutiae, truce inferiae, sacrifices for the dead insidiae, ambush lactes, instestines lamenta, lamentations lautomiae, stone quarries liberi, children manes, dead spirits (friendly) manubiae, spoils minae, threats moenia, -ium town-wall nundinae, market nuptiae, wedding palpebrae, eyelids parentalia, festival of dead relatives	parietinae, ruins penates, house-hold gods phalerae, trappings praecordia, -ium, midriff, diaphragm praestigiae, juggler's tricks preces, -um, prayer primitiae, first fruits quisquiliae, rubbish reliquiae, remains renes, kidneys salinae, salt-pits scalae, stairway sentes, brambles spoila, -orum, spoils sponsalia, -ium, betrothal suppetiae, succor talaria, -ium, winged sandals tenebrae, darkness thermae, warm baths tonsillae, tonsils tormina, colic tricae, tricks utensilia, -ium, necessary things valvae, folding doors verbera, -um, scourging vindiciae, legal claim virgulta, -orum, shrubbery viscera, entrails

Some defective nouns change meaning in their plural forms.

Nouns That Change Meaning
aedes, -is, temple aqua, water auxilium, help carcer, prison castrum, fort cera, wax comitium, assembly place copia, abundance delicium, pleasure facultas, capability finis, end, limit fortuna, fortune, luck habena, strap, thong impedimentum, hindrance littera, letter ludus, game opera, work pars, part rostrum, beak sors, lot tabula, board, tablet vigilia, a nightwatch	aedes, house, palace aquae, mineral springs auxiliae, auxiliaries, reinforcements carceres, barriers castra, camp cerae, waxen tablets comitia, voting assemblies copiae, forces, troops deliciae, darling, pet facultates, goods fines, territories, boundaries fortunae, possessions habenae, reins impedimenta, baggage litterae, letters, writings ludi, public games operae, workmen partes, parts, role rostra, speaking platform in the forum sortes, oracle tabulae, tablets, accounts vigiliae, pickets

Some nouns occur only in some cases.
ex.: vis, vi, vim, f., force.

Peculiar Nouns

Some nouns just have odd or peculiar stems.

Peculiar Nouns
as, assis, a copper auceps, aucupis, a fowler bos, bovis, cow gen.pl: boum Dat & Abl. pl: bubus, bobus caput, capitis, head anceps, ancipitis, two-headed preaceps, praecipitis, headlong caro, carnis, flesh Ceres, Cereris, Ceres far, farris, spelt fel, fellis, gall femur, femoris or feminis, thigh	iter, itineris, journey iecur, iecoris, liver other gens: iecinoris, iecineris, iocineris Iuppiter, Iovis, Jupiter mel, mellis, honey nix, nivis, snow os, ossis, bone os, oris, mouth pollis, pollinis, flour sanguis, sanguinis, blood senex, senis, old man supellex, supellectilis furniture Venus, Veneris, Venus