Irregular plurals

This page contains lists of words whose plurals are acceptable only in the irregular form. For example, the ODE admits 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.

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

• ANACRUSIS, ANAMNESIS, ANKYLOSIS, APOPHYSIS, CARYOPSIS, CATALYSIS, CHLOROSIS, COREOPSIS, DIAERESIS, DIAGNOSIS, DIAPHYSIS, DIATHESIS, EPIPHYSIS, EXOSTOSIS, HEMIPENIS, HOMOEOSIS, KERATOSIS, LIPIDOSIS, OVOTESTIS, PARABASIS, PARALYSIS, PERIAPSIS, PROGNOSIS, PROLEPSIS, PROTHESIS, PSYCHOSIS, PYROLYSIS, SCLERITIS, SUFFRAGIS, SYLLEPSIS, SYMBIOSIS, SYMPHYSIS, SYNERESIS, TSESSEBIS.
• ANABASIS, ANALYSIS, APODOSIS, DIALYSIS, DIEGESIS, ELLIPSIS, EXEGESIS, HOMEOSIS, NEUROSIS, ORTHOSIS, PROTASIS, STENOSIS, SYNAPSIS, VENTURIS, ZOONOSIS.
• CHASSIS, ENTASIS, 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.

-OT

There are no exclusively -OT plurals, although there are some words like SHALLOT which might spuriously be imagined as irregular plurals.

Italian plurals

-O to -I

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