... in `-o' add `-s', and some add `-es'.
photo* photos piano* pianos
hero* heroes potato* potatoes
Nouns ending in a consonant and `-y' change to `-ies'.
country* countries ... adjective.
`-le' changes to `-ly':gentle * gently
`-y' changes to `-ily':easy * easily
`-ic' changes to `-ically':automatic * automatically
`-ue' changes to `-u...