In “Punctuation Points: Possessing the Apostrophe,” I outlined the three main uses for the apostrophe:
- Showing possession for a noun
- Indicating the omission of some letters in a word or numbers in a year
- Showing plurality of single letters, single numbers, and abbreviations
Today, I’ll review more advanced rules for using the apostrophe to show possession, as well as the rules for showing omission and plurality.
More Cases for Using the Possessive Apostrophe
Double possessive (or double genitive): In some cases, use of and an apostrophe in same phrase.
Joint possessive: Use the apostrophe only on the last item in a series of elements when the elements own something together.
Possessives of possessive names: If a proper noun is already a possessive, you do not need to add another apostrophe s. You can either recast the sentence or use the original possessive name.
Units of measurement: The unit gets an apostrophe when it modifies a noun.
Whew! Now that we have the possessive apostrophe out of the way, let’s quickly run through the two other apostrophe rules.
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The Omission Apostrophe
The apostrophe is also used to make contractions:
The Plural Apostrophe
Finally, the apostrophe is sometimes used to make single letters, single numbers, and abbreviations plural:
Sean got all A’s on his report card.
Disco was popular in the 1970’s.
The CEO’s are meeting after the VP’s.
Whether you use the apostrophe to form plurals in these cases depends on your style guide. Here are some of the popular ones:
- The Chicago Manual of Style: For capital letters, numerals, and abbreviations, add s; for lowercase letters, add apostrophe s.
- The AP Stylebook: For numerals, abbreviations, and multiple letters (e.g., VIP), add s; for single letters, add apostrophe s.
- APA: For single letters, numbers, and abbreviations, add s (except for p.; its plural is pp.).
But you should never form a plural noun with an apostrophe s:
Wrong: The car’s are on the track.
Right: The cars are on the track.
And those are the advanced apostrophe rules. Did I answer all your questions on the apostrophe? If not, put your concerns in the comments below and I’ll try to answer them.
A version of this article originally published on The Writing Resource.