The apostrophe has three uses:

1. To form possessives of nouns
2. To show the omission of letters
3. To indicate certain plurals of lowercase letters

Forming Possessives of Nouns

To see if you need to make a possessive, turn the phrase around and make it an “of the…” phrase. For example:

the boy’s hat = the hat of the boy

three days’ journey = journey of three days

If the noun after “of” is a building, an object, or a piece of furniture, then no apostrophe is needed!

room of the hotel = hotel room
door of the car = car door
leg of the table = table leg

Once you’ve determined whether you need to make a possessive, follow these rules to create one.

• add ‘s to the singular form of the word (even if it ends in -s):
  

  the owner’s car
  James’s hat (James’ hat is also acceptable. For plural, proper nouns that are possessive, use an apostrophe after the ‘s’: “The Eggleses’ presentation was good.” The Eggleses are a husband and wife consultant team.)

  NOTE: the generally accepted convention for most academic styles (including CMOS, APA, and MLA) is to add apostophe + s to the singular form of the word, even if it ends in “s.” Non-academic styles, such as AP, suggest simply adding an apostrophe to the end of a word that ends in “s.” Please check the style guide of whatever format you’re using to make sure you’re in line with their recommendations.

• add ‘s to the plural forms that do not end in -s:
  

  the children’s game
  the geese’s honking

• add ‘ to the end of plural nouns that end in -s:
  

  two cats’ toys
  three friends’ letters
  the countries’ laws

• add ‘s to the end of compound words:
  

  my brother-in-law’s money

• add ‘s to the last noun to show joint possession of an object:
  

  Todd and Anne’s apartment

View Complete Article

EXERCISE: Try this Practice to see what you learned about Apostrophes. Click here for practice exercise