If you mean only a single s, it attaches to most nouns to make them plural (boy, boys), although some noun plurals are irregular (child, children; sheep, sheep). It also attaches to the third-person singular present-tense verb: I eat, you eat, he eats, we eat, you (plural) eat, they eat. Note that the only subject-verb agreement error a person can make is to forget the s on the third person singular or to put it on any other verb.
An s with an apostrophe ('s or s') attaches to a common noun or proper noun to show possession: the rug's color; Mary's book. If the noun is singular, the apostrophe comes first; if it is plural, then the apostrophe comes after the s that is making the noun plural: a boy's dog; these boys' dog. If the plural noun doesn't end with s, use 's: the children's toys.
I hope this helps!
Maria Batty (admin)
I just noticed your attachment. Did you have a question about that?