Rules for the Plural
add 's' to the word unless it fits in any of the following categories:
-f or -fe= -ves (self= selves / life= lives)
-o -x -s -ss -sh -ch -zz add -es (tomato= tomatoes / box= boxes / bus= buses / kiss= kisses / brush= brushes / watch= watches / buzz= buzzes)
-y add -ies (fly= flies) *Except when Vowel before Y: boy= bOYs)
irregular ones (do not follow an specific rule): deer= deer / foot= feet / woman= women / man= men / crisis= crises / salmon= salmon / fish= fish* / ox= oxen / mouse= mice / goose= geese / person= persons & people* / louse= lice / bison= bison / erratum= errata / medium = media / bison= bison / child= children / oasis= oases / penny= pence /.
For those who need to brush up on their English grammar, need to keep up or simply need an easy reference, here you are a simple outline of some of the English Rules for the Plural:
* Of course there are MANY others, so please feel free to submit any omission.