Simple solution:

If last character = 's'
Add 'es'
else
Add 's'
Endif

>Hey there!
>
>Does anybody know where I can find some code that takes a English word in singular form and returns the plural, and vice-versa?
>
>I'm not looking for anything bulletproof... it just has to cover the simple/medium scenarios (I'm not worrying about things like mouse/mice or child/children, for instance).
>
>TIA