A possessive form of a word is one that shows ownership, origin or a relationship tie.

In English most possessives are shown by "apostrophe s". Examples are

  • Carol's bike
  • New York's skyline (some people say it's better to show the relationship of objects by spelling it out like "skyline of New York")
  • Mike's sister-in-law

These could all be written out in other ways, such as

  • the bike owned by Carol
  • the skyline of New York
  • the sister-in-law of Mike

There is some debate about whether to have the s at the end when the base word ends in s. Should it be Tess's shoulder or Tess' shoulder? There are arguments and grammarians who believe each option.

Then there are possessive pronouns, which are often confused with other words. Their means something possessed by them. They're is a contraction for they.