The following are four simple rules to remember when using the apostrophe in writing.
1) To indicate possession, place an apostrophe followed by the letter “s” after the name of the person or the thing doing the possessing. For example, “John’s book” or “the apple’s color”.
2) If the name or thing doing the possessing ends in an “s”, simply add an apostrophe to the end of the word to indicate possession. For example, “James’ book” or “the business’ location”.
3) To indicate possession for multiple things ending in an “s”, simply add an apostrophe. For example, “the bird’s color” would indicate the color of a single bird while “the birds’ color” would indicate the color of multiple birds.
4) It’s is a special case since it can either be a condensation of “it is” or the possessive of “it”. Therefore the rule changes. “Its” without the apostrophe is possessive while “it’s” with the apostrophe is the condensation of “it is”.
I’ll see you in the classroom,