Plural of Inconsistency
mouse -> mice
louse -> lice
die -> dice
house -> houses
spouse -> spouses
grouse -> grouse
spice -> spices
tooth -> teeth
goose -> geese
foot -> feet
book -> books
boot -> boots
beet -> beets
cactus -> cacti
nucleus -> nuclei
bolus -> boli
radius -> radii
fungus -> fungi
graffito -> graffiti
biscotto -> biscotti
libretto -> libretti
concerto -> concerti
locus -> loci
focus -> foci
bacillus -> bacilli
syllabus -> syllabi
stimulus -> stimuli
lotus -> lotuses
virus -> viruses
alumnus -> alumni
alumna -> alumnaea
antenna -> antenae
formula -> formulae
lacuna -> lacunae
nebua -> nebulae
curriculum -> curricula
datum -> data
erratum -> errata
stratum -> strata
corpus -> corpora
opus -> opera
ovum -> ova
referendum -> referenda
criterion -> criteria
anlysis -> analyses
oasis -> oases
thesis -> theses
crisis -> crises
ellipsis -> ellipses
parenthesis -> parentheses
codex -> codices
vortex -> vortices
vertex -> vertices
axis -> axes
axe -> axes
medium -> media
loaf -> loaves
self -> selves
elf -> elves
scarf -> scarves
half -> halves
thief -> thieves
wife -> wives
wharf -> wharves
wolf -> wolves
ox -> oxen
matrix -> matrices
child -> children
man -> men
woman -> women
bureau -> bureaux
beau -> beaux
chateau -> chateaux
tableau -> tableau
mother-in-law -> mothers-in-law
attorney general -> attorneys general
child-in-law -> children-in-law
major general -> major generals
bison -> bison
buffalo -> buffalo
deer -> deer
faux pas -> faux pas
fish -> fish
craft -> craft
offspring -> offspring
salmon -> salmon
series -> series
sheep -> sheep
swine -> swine
trout -> trout
tuna -> tuna
The pural of octopus is clearly hexadecapod.