Irregular plurals

This page contains lists of words whose plurals are acceptable only in the irregular form. For example, Oxford Dictionaries Premium 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.

These are considered separately from -OS or -OES.

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

Latin plurals

-A to -AE

• AMYGDALA, BLASTULA, BRANCHIA, CATHEDRA, 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, SPICULA, 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, CAUDA, 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 -ES

• FOLLIS, TESTIS, UNGUIS.
• NARIS, PUBIS.
• AXIS.

-IS to -IDES

• RHACHIS.
• RACHIS.
• APHIS, APSIS.

-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.

Greek plurals

-IS to -ES

• ENTASIS, GENESIS, KINESIS, MEIOSIS, MITOSIS, MYCOSIS, NEMESIS, OSMOSIS, PARESIS, SOROSIS.
• CRASIS, CRISIS, THESIS, TMESIS.
• ARSIS, BASIS, OASIS, TAXIS.

-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.
• DEMOS, TELOS, TOPOS.
• NAOS.

Other

• POLIS → POLEIS
• URAEUS → URAEI

Latin and Greek

• CADUCEUS → CADUCEI
• RAPHE → RAPHAE

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

• ANTIPASTO, PAPARAZZO, SGRAFFITO, SOLFEGGIO, TRAGHETTO
• AMORETTO, CASTRATO, CORNETTO, GRAFFITO, TENORINO.
• MAFIOSO, SALOTTO, SECONDO, SORDINO, STRETTO.
• GELATO, PANINO.
• OVOLO, PUTTO, SCUDO, SOLDO, TONDO.

Monetary unit plurals

• AGORA → AGOROT, AGOROTH (Israel)
• BAN → BANI (Romania)
• COLÓN → COLONES (Costa Rica and El Salvador)
• FENING → FENINGA (Bosnia and Herzegovina)
• GROSZ → GROSZE, GROSZY (Poland)
• KRONE → KRONER (Denmark and Norway)
• KROON → KROONI (Estonia)
• LAT → LATI (Latvia)
• LEU → LEI (Romania)
• LIKUTA → MAKUTA (formerly the Democratic Republic of the Congo)
• LIRA → LIRE (Italy and Turkey)
• LOTI → MALOTI (Lesotho)
• METICAL → METICAIS (Mozambique)
• PAISA → PAISE (India, Nepal and formerly Pakistan)
• PENNI → PENNIÄ (Finland)
• QINTAR → QINDARKA (Albania)
• REAL → REAIS (Brazil)
• SENTE → LISENTE (Lesotho)
• SOL → SOLES (Peru)
• STOTINKA → STOTINKI (Bulgaria)

Other

• FEIS → FEISEANNA (Irish)
• PULI → PULIK (Hungarian)