Irregular Plural Nouns (List and Examples)

Knowledge of irregular plural nouns is very important, especially in relation to the rules of use of subjects and predicates/verbs. 

The relationship of Subject to Verb is very close, namely to determine whether the verb is made plural or singular, you must know whether the subject is plural or singular.

Generally, nouns are regular, i.e. nouns which are plural in nature, only given an additional -s, -es, or –ies. However, there are a number of irregular verbs which are verbs whose plural form does not use affixes -s, -es, or –ies, but changes in spelling, but also sometimes does not change at all that is the same between the singular and plural forms. See the following table:

Irregular plural nouns list and examples

US -> I
The word ending in US changes to the ending I :

SINGULARPLURAL
alumnusalumni
cactuscacti
focusfoci / focuses
fungusfungi / funguses
nucleusnuclei
radiusradii
stimulusstimuli

Example of usage:
1. The fungus is dangerous (singular)
2. The fungi are dangerous (plural)
3. The fungus endangers everyone (singular)
4. The fungi endanger everyone (plural)

IS -> ES

SINGULARPLURAL
axisaxes
analysisanalyses
basebases
crisiscrises
diagnosisdiagnoses
ellipsisellipses
hypothesishypotheses
oasisoases
paralysisparalyzes
parenthesisparentheses
synthesissyntheses
synopsissynopses
thesistheses

See also:
Types of Nouns, Collective Nouns, Uncountable Nouns,

IX -> ICES

SINGULARPLURAL
appendixappendices
indexindices / indexes
matrixmatrices / matrixes

EAU -> EAUX

SINGULARPLURAL
beaubeaux
bureaubureaus / bureaux
tableautableaux / tableaus

*** -> EN
Sign *** means that the word does not have special indicators / features:

SINGULARPLURAL
childchildren
manmen
oxoxen
womanwomen

*** -> A

SINGULARPLURAL
bacteriumbacteria
corpuscorpora
criterioncriteria
curriculumcurricula
datumdata
genusgenera
mediummedia
memorandummemoranda
phenomenonphenomenon
stratumstrata

NO CHANGE
Some of the following nouns have the same form between singular and plural or there is no change at all :

SINGULARPLURAL
deerdeer
fishfish
meansmeans
offspringoffspring
seriesseries
sheepsheep
speciesspecies

OO -> EE

SINGULARPLURAL
footfeet
goosegeese
toothteeth

A -> AE

SINGULARPLURAL
antennaantennae / antennas
formulaformulae / formulas
nebulanebulae
vertebraevertebrae
vitavitae

OUSE -> ICE

SINGULARPLURAL
louselice
mousemice

You don’t need to memorize all the nouns in the tables above, enough you remember/recognize the ending forms and their changes/additions when becoming plural. Especially for nouns that are the same singular and plural, such as Sheep> sheep , you need to memorize them.

irregular verb list
List of irregular verbs