Most common irregular plural nouns

addendum	addenda or addendums
aircraft	aircraft
alumnus	alumni
analysis	analyses
antenna	antennae or antennas
apex	apices or apexes
appendix	appendices or appendixes
axis	Axes
bacillus	Bacilli
bacterium	Bacteria
basis	Bases
bison	Bison
bureau	bureaux or bureaus
cactus	cacti or cactus or cactuses
child	Children
corpus	Corpora
crisis	Crises
criterion	criteria or criterions
curriculum	curricula or curriculums
datum	Data
deer	deer or deers
diagnosis	Diagnoses
die	dice or dies
dwarf	dwarves or dwarfs
ellipsis	Ellipses
erratum	Errata
faux pas	faux pas
fish	fish or fishes
focus	foci or focuses
foot	feet or foot
formula	formulae or formulas
fungus	fungi or funguses
half	halves
hoof	hooves or hoofs
hypothesis	hypotheses
index	indices or indexes
larva	larvae or larvas
loaf	loaves
louse	lice
man	men
matrix	matrices or matrixes
medium	media or mediums
memorandum	memoranda or memorandums
mouse	mice
nebula	nebulae or nebulas
nucleus	nuclei or nucleuses
oasis	oases
offspring	offspring or offsprings
ovum	ova
ox	oxen or ox
parenthesis	parentheses
phenomenon	phenomena or phenomenons
quiz	quizzes
radius	radii or radiuses
referendum	referenda or referendums
salmon	salmon or salmons
scarf	scarves or scarfs
self	selves
series	series
sheep	sheep
species	species
stimulus	stimuli
swine	swine
syllabus	syllabi or syllabuses
synopsis	synopses
tableau	tableaux or tableaus
thesis	theses
thief	thieves
tooth	teeth
trout	trout or trouts
tuna	tuna or tunas
vertebra	vertebrae or vertebras
vertex	vertices or vertexes
vita	vitae
vortex	vortices or vortexes
wharf	wharves or wharfs
wife	wives
wolf	wolves
woman	women

courtesy : thoughtco.com