Rule 1a. Use the apostrophe to show possession. To show possession with a singular noun, add an apostrophe plus the letter s. Rule 1b. Many common nouns end in the letter s ( lens, cactus, bus, etc.). So do a lot of proper nouns ( Mr. Jones, Texas, Christmas ).

Rule #1: Use an apostrophe + -s at the end of a noun to show singular possession of something. When a single someone or something has possession of another object, you simply add an apostrophe -s to the end of the word. If the possessive noun already ends in an -s, you have a choice concerning the apostrophe placement.

The rules for apostrophes are very simple. What you need to do is to decide whether possessive noun is plural or singular as well as whether or not it will end in “s”. Rule one: If possessive noun is singular, then you need to add apostrophe plus “s”.