Irregular Noun Plurals
When the final -y is preceded by a consonant, change the -y to -i and add -es:
baby-->babies lady-->ladies
If a noun ends in -fe or -f, the ending is changed to -ves (except: beliefs, chiefs, roofs, staffs).
life-->lives thief-->thieves
Add -es to nouns ending in -sh, -ch, -s, -z, and -x. (Exceptions: monarchs, stomachs.)
wish-->wishes class-->classes
Both the -s and -es spellings are accepted for nouns ending in -o.
tomato-->tomatoes hero-->heroes
The plural possessive form of these nouns is also irregular.
child-->children foot-->feet goose-->geese man-->men tooth-->teeth
The plural is the same as the singular for these nouns.
deer-->deer fish-->fish sheep-->sheep species-->species
The final sound of these plurals is pronounced like the word sees. crisis-->crises thesis-->theses
