Apostrophes Explained

            Writers seem to become more frustrated and confused by apostrophes than any other punctuation mark. Apostrophes are an important part of English, which makes correct usage imperative. Instead of guessing at where an apostrophe should go, you can confidently use this punctuation by remembering their three main functions.

Function #1: Possession

            The first function, and most common, is creating the possessive form of words. Writers show possession by either adding an apostrophe or an apostrophe with an s to a word. Which one you choose depends on who is doing the possessing. If you have a singular noun, you need to add the apostrophe with an s. An example is “Tom’s books.” If you have a plural noun, you need to add only an apostrophe. An example of this is “the boys’ books.”

There are two exceptions to this rule. The first applies to singular words that end with an s, such as James. You could write them with just an apostrophe, but for the sake of clarity, several style guides recommend that you use the apostrophe with an s. In my writing, I decide case-by-case. I’m more old school in my preferences for punctuation, which means I often use only an apostrophe. I will sometimes add the s if I think it necessary for clarity’s sake. For example, you can write either “James’ book” or “James’s book.” Unless you are following a style guide, you should choose whichever you prefer and stay with it.

The second exception involves plural words that are formed without an s, such as children or mice. These words are treated like they are singular and receive an apostrophe with an s. The best way to remember this is that if it doesn’t already have an s, you will need to add one to make it possessive.

Function #2: Contractions

            The second function of apostrophes is creating contractions. English-speakers are adept at contracting their words and omitting letters when they speak. To replicate that in writing, apostrophes indicate places where the writer omitted letters. For contractions, the apostrophe will often go towards the end of the word. So, for instance, “I don’t have that book.” The apostrophe indicates that “do not” has been contracted into one word with the o removed.

Apostrophes can also indicate the omission of letters elsewhere in a word. For example, “That cake is lookin’ good.” The apostrophe takes the place of the omitted g. In these situations, the apostrophe goes wherever you omitted letters.

Contractions and other omissions can be useful to make writing have the same natural flow of speech. However, you want to keep track of how many contractions you are using. Too many can change the tone of your writing and make it hard to read.

Function #3: Plurals

            The final function of apostrophes is a lot less common than the other two and much more controversial. An apostrophe can be used occasionally to create a plural. This most often happens with numbers, letters, and symbols.

Depending on which style guide you consult, the advice will differ greatly. One rule everyone seems to agree on is how to create the plural form of lowercase letters. When talking about letters, you should use the apostrophe with an s. For example, “You forgot to dot your i’s.” Without the apostrophe, the sentence would not make sense because there would be little indication that it is a letter and not a word.

With abbreviations, capital letters, and numbers, advice becomes more varied. You can add the apostrophe with an s to create the plural. They would look like this: MRI’s, I’s, 1800’s. You can also go without the apostrophe, which seems to be the more popular way. In that case, those same words would look like this: MRIs, Is, 1800s.

Which form you choose will depend heavily on meaning and clarity, as you can see from the example. If you aren’t careful, a reader might misinterpret your plurals as indicating possession, or as a different word than you intended. If you must use a style guide, reference which version the guide prefers. Otherwise, I suggest choosing one form and staying with it.


            If you can remember these three functions and how to apply them, you will have no problems with apostrophes. The application of apostrophes relies on the sentence’s meaning and structure. If you follow the simple rules and remember the importance of clarity, you will know where an apostrophe is necessary without hesitation. As with all parts of writing, don’t be afraid to look it up. It is always better to check rather than depend on memory.

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