plural=?>1 1 cat=cat 2cat=cats 1dog=dog 2dog=dogs word+s=plural (number>1 cat+s=cats cats=more than 1 cat word+s=plural friend+s=friends friends=more than 1 friend

Well, there are many examples but I think you refer to possession. Look at this: if we want to show possession we add: singular noun + 's :This is my father's car singular noun-s + ' : This is my boss' office plural noun + ' : This is my parents' room irregular plural + 's : This is the children's room and 's to the last noun of a phrase: Ann and John's ball.

I'm not sure what you are asking. Can you give an example? Are you asking about "s" to make a noun plural, or "s" to make something possessive?