--s:bird,shop,lake,dog,sea
ch,sh,s,x--es:church,dish,class,box,watch
y--ies:factory,fly,family,baby,university
o--es:tomato,hero,potato,echo,domino
f,fe--ves:leaf,thief,shelf,knife,life
f,fe--s:belief,cliff,gulf,proof,fife
o--s:piano,photo,memo,solo,soprano
不规则变化:tooth--teeth,foot--feet,goose--geese,ox--oxen,mouse--mice
单复数同行:cattle,means,deer,fish,bison