Some word plural

Singular- Plural

hero-heroes
belief-beliefs
goose-geese
life-lives
ox-oxes
happiness-happiness
mouse-mice
thief-thieves
milk-milk
country-countries
stool-stools
chalk-chalks
rubbish-rubbish
wastepaper basket-wastepaper baskets
blackboard-blackboards
man-mencake-cakescup-cups

hero heroes

belief = same

goose geese

life lives

ox oxen

happiness= same

mouse mice

thief thieves

milk = same

country countries

stool stools

chalk = same

rubbish = same

wastepaper basket .... baskets

blackboard blackboards

man men

cake cakes

cup cups

abstract nouns do not have plural form so they are the same.

YuPan Ching：
hero-------heroes
belief------beliefs
goose-----geese
life----------lifes
ox----------oxen
happiness-----no plural
mouse----mice
thief--------thieves
milk--------no plural
country---countries
stool-------stools
chalk------no plural
rubbish---no plural
wastepaper basket---wastepaper baskets
blackboard----blackboards
man-------men
cake-------cakes
cup---------cups

The plural of ox is OXEN. (Not oxes)