offers hundreds of practice questions and video explanations. Go there now.
Sign up or log in to Magoosh TOEFL Prep.

Apostrophes and Possessive Nouns, Part 1: Apostrophe Before S

Today we’re going to talk about the apostrophe, the punctuation in English (and some other languages) that looks like this: /’/. Apostrophes are used in contractions to indicate that some letters have been left out of a word or phrase. For example, there is an apostrophe in “don’t,” which is short for “do not.” Apostrophes are also used in possessive words that indicate ownership of something or a special connection to something.

The use of apostrophes in possessives is a little more complicated than the use of this kind of punctuation in contractions. Sometimes possessive words have an apostrophe followed by the letter s. At other times, possessives place the apostrophe after the letter s. Here in Part 1 of this series, we’ll look at the times when you should use apostrophes before the letter S.


Apostrophes before the letter S

  • Rule 1: To show possession, add an apostrophe followed by an s to the end of a singular noun that does not normally end in s.
    • Example 1: You are reading one of David’s blog posts.
      (“David” is a proper noun that doesn’t end in s, so to make this name possessive, you change it to David’s.)
    • Example 2: The moon’s light is really just a reflection of the light from the sun.
      (“Moon” is a common noun not ending in s. An apostrophe and an s must be added to the end of the word to create the possessive form moon’s.)
  • Rule 2: An apostrophe followed by an s should also appear at the end of irregularly-formed plural nouns that don’t normally end in s.
    • Example 1: Seuss is a famous American children’s book author.
      (“Children” is the plural for “child.” To indicate that something belongs to children or is for children, change the word form to children’s, with an apostrophe at the end.)
    • Example 2: The shape, size, and length of cacti’s needles vary depending on the species of cactus.
      (“Cacti” is the irregularly-formed plural of the word cactus. To show that something belongs to cacti or is closely associated with more than one cactus, use an apostrophe and an s to create the possessive word cacti’s.)


The rules above mark the two situations where you should use both an apostrophe and an s at the end of a possessive noun. There are two other situation where possession is shown by adding only an apostrophe at the end of the word, without also adding an s. In my next post on this subject, we’ll look at the two rules for possessives that end in apostrophe-only.