Irregular plurals

This page contains lists of words whose plurals are acceptable only in the irregular form. For example, Oxford Dictionaries Online and Lexico admit only VERTEBRAE and not VERTEBRAS as the plural of VERTEBRA, so VERTEBRA is listed under the section -A to -AE. Words are listed up to the length at which their regular plural would be nine letters or fewer, so for example we do not list TRAPEZIUS even though the plural is exclusively TRAPEZII because no one needs to know that TRAPEZIUSES is not valid.

These are considered separately from -OS or -OES.

The words are sorted by etymology, formation rule, length and then alphabetically.

Note that this list has not yet been fully verified, so some spurious entries may remain; e.g. DIVIDES is not really the plural of DIVIS!

Latin plurals

-A to -AE

• AMYGDALA, BLASTULA, BRANCHIA, CERCARIA, FENESTRA, GASTRULA, GLABELLA, INCISURA, MAMMILLA, PETECHIA, SHIGELLA, STROBILA, TRICHINA, TROCHLEA, VERTEBRA.
• AMPULLA, CHALAZA, COCHLEA, CYPSELA, FAMILIA, FILARIA, FIMBRIA, FURCULA, LAMELLA, MAMILLA, MAXILLA, MINUTIA, MONILIA, OOTHECA, PAPILLA, PATELLA, PHALERA, PLANULA, SCOPULA, SEQUELA, SILIQUA, TESSERA.
• ALUMNA, APHTHA, AREOLA, AXILLA, CHAETA, CLOACA, CONCHA, CRISTA, EPHYRA, EXEDRA, FACULA, FIGURA, HYDRIA, INFULA, INSULA, INTIMA, LAGENA, LAMINA, LIGULA, LUNULA, MACULA, MORULA, MUCOSA, PAPULA, PATERA, PLEURA, PUNCTA, RADULA, SCORIA, STRUMA, TEGULA, TORULA, TUNICA.
• ALULA, BULLA, CELLA, COSTA, FOVEA, FURCA, GEMMA, HYPHA, LARVA, LIBRA, MEDIA, PALEA, PELTA, PINNA, SCOPA, SELLA, STELA, STRIA, SUMMA, TESTA, THECA, UVULA, VIRGA, VITTA.
• ALGA, COXA, GENA, PUPA, SETA.

-IS to -IDES

• RACHIS.
• APHIS, APSIS, DIVIS.

-IX/-EX to -ICES

• RECTRIX, TECTRIX, TORTRIX, VICTRIX.
• CAUDEX, CERVIX, CORTEX, FORNIX, POLLEX, SCOLEX, SPADIX.
• CAREX, CULEX, HELIX, RADIX, VARIX.

-UM to -A

• ABOMASUM, ADDENDUM, ALLODIUM, BASIDIUM, CEREBRUM, CIBORIUM, CINGULUM, COAGULUM, CONIDIUM, CYATHIUM, EXEMPLUM, HYMENIUM, HYPOGEUM, INDUSIUM, INOCULUM, LABELLUM, MOMENTUM, MYCELIUM, OOGONIUM, PATAGIUM, PERIDIUM, PERINEUM, PUDENDUM, PUPARIUM, PYGIDIUM, PYXIDIUM, REFUGIUM, RESIDUUM, SCHOLIUM, SOLATIUM, SPECTRUM, SPECULUM, STRIATUM, SUDARIUM, SYCONIUM, TOMENTUM, VASCULUM, VELARIUM, VEXILLUM, VIATICUM, VINCULUM, VIVARIUM.
• ARCANUM, BACULUM, ERRATUM, ISCHIUM, LITHIUM, OMENTUM, OPPIDUM, ORGANUM, OSCULUM, PINETUM, PUNCTUM, QUANTUM, SISTRUM, STRATUM, THORIUM.
• ADYTUM, ANTRUM, CAECUM, CILIUM, DAMNUM, DORSUM, FOLIUM, GRANUM, LABIUM, LABRUM, MILIUM, OIDIUM, OMASUM, OSTIUM, PHYLUM, SCUTUM, SENSUM, SEPTUM, SIGLUM, TERGUM, UNICUM.
• DATUM, DURUM, HILUM, ILEUM, ILIUM, JUGUM, NOTUM, RHEUM, VELUM.
• OVUM.

-US to -I

• ALUMNUS, ANNULUS, CALAMUS, CANTHUS, CLYPEUS, CUMULUS, EMBOLUS, FAMULUS, FLOCCUS, GLUTEUS, HAMULUS, HUMERUS, INCUBUS, LIMULUS, LOCULUS, MALLEUS, MODULUS, NUCLEUS, OCELLUS, PERITUS, PLUTEUS, POLYPUS, PYLORUS, SILENUS, SOLIDUS, THALLUS, THYRSUS, TUMULUS.
• ACINUS, AMICUS, AUREUS, CARPUS, CERCUS, CIRRUS, COCCUS, DUCTUS, FUNDUS, LIMBUS, MYTHUS, NAEVUS, OBELUS, OCULUS, PALPUS, PAPPUS, PILEUS, RECTUS, SAMFUS, SULCUS, TARSUS, THYMUS, TOPHUS, TRAGUS, URAEUS, VILLUS, XYSTUS.
• ASCUS, CONUS, FUCUS, GYRUS, HILUS, KORUS, KURUS, LOCUS, MAGUS, NODUS, RAMUS, SOLUS, SORUS, TABUS, VAGUS, VICUS.
• TAUS.

-US to -ERA

• VISCUS.
• GENUS, SOLUS.

Greek plurals

-IS to -ES

• CHASSIS, ENTASIS, GENESIS, KINESIS, MEIOSIS, MITOSIS, MOPANIS, MYCOSIS, NEMESIS, OSMOSIS, PARESIS, SOROSIS, TZIMMIS.
• COMBIS, CRASIS, CRISIS, FOLLIS, FORTIS, GRATIS, LATHIS, LUNGIS, MURRIS, PADRIS, PASTIS, SEPSIS, TACHIS, TESTIS, THESIS, TMESIS, UNGUIS.
• ANTIS, APSIS, ARSIS, BASIS, BIDIS, CEDIS, DELIS, DENIS, DIVIS, GALIS, HOKIS, IDLIS, LARIS, LYSIS, MALIS, MAXIS, MINIS, NARIS, NONIS, OASIS, PALIS, PERIS, PIPIS, POLIS, PUBIS, SAKIS, SATIS, SEMIS, TAPIS, TAXIS, TIKIS, TOPIS, WADIS, WALIS.
• AXIS, FEIS, HUIS, LEIS.

-MA to -MATA

• CHIASMA.
• STEMMA, STROMA, ZYGOMA.
• TAGMA.

-NX to -NGES

• PHARYNX.
• LARYNX, MENINX.

-ON to -A

• APHELION, EPYLLION, NOUMENON, OSTRACON, OSTRAKON, PARERGON.
• ELYTRON, EPIZOON, PLEURON, SILICON.
• LOGION, XOANON.
• BORON, TAXON.
• ANON.

-OS to -OI

• OMPHALOS.
• PRONAOS, TEMENOS.
• DROMOS, KOUROS, MYTHOS, PITHOS, THOLOS.
• TELOS, TOPOS.
• NAOS.

French plurals

-EAU to -EAUX

• BANDEAU, CHAPEAU, MORCEAU, RONDEAU, TABLEAU, TRUMEAU.
• BATEAU, RESEAU.

Hebrew plurals

-IM

• KIBBUTZ, SHOCHET.
• HAZZAN, MINHAG, MINYAN, MOSHAV, SIDDUR.
• DAYAN, SHIUR.

Italian plurals

-O to -I

• AMORETTO, CASTRATO, CORNETTO, GRAFFITO, TENORINO.
• MAFIOSO, SALOTTO, SECONDO, SORDINO, STRETTO.
• GELATO, MODULO, PANINO.
• OVOLO, PUTTO, SCUDO, SOLDO, TONDO.
• TORO.

Monetary unit plurals

The plural of LOTI, the currency of Lesotho, is MALOTI; the plural of SENTE, one hundredth of a loti, is LISENTE. The plural of LIKUTA, the former currency of Zaire, is MAKUTA. The plural of METICAL, one hundredth of a centavo, is METICAIS.