An apostrophe - ' - is used in a variety of ways in English in order to:
- Show that someone possesses something
- Omit a letter in a word or in a contraction of a verb form
Apostrophes for Possession
An apostrophe is most commonly used directly after a person's name to indicate posession followed by an "s". However, there are a number of exceptions to this rule based on whether the apostrophe is used with a singular or plural noun. Here are the rules:
Use with Singular Nouns
Use an apostrophe placed directly after a singular noun followed by an "s". The most common use of this form is with proper names. However, this form may also be used with nouns referring to people, and to show the properties of an object.
I rode John's bicycle yesterday.
Jennifer's house has a beautiful garden.
With Nouns Referring to People
The student's book was on the table.
You can find the employer's address on the website.
The car's color is green.
Our school's building is in central Portland.
Use with Regular Plural Nouns
An apostrophe may also be used with a regular plural noun referring to people or to objects. With regular plural nouns, place the apostrophe directly after the "s" of the plural. No further "s" is required.
With Nouns Referring to People
The students' test results were impressive.
All of our employees' family members receive health care benefits.
Those books' authors are from Germany.
The smart phones' service provider charges a lot of money for data usage.
Use with Irregular Plural Nouns
Irregular plural nouns use an apostrophe in a similar manner to singular nouns. Place the apostrophe after the irregular plural followed by an "s".
The women's soccer team has done very well this year.
I'll take them up to the children's bedroom.
Use with Time, Distance and Other Values
An apostrophe can also be used with a specific time, distance, measurement and so on. In this case, follow the rules for singular or plural nouns. For the singular, place the apostrophe at the end of the time, distance or other measurement followed by an "s". For plural nouns, place the apostrophe at the end of the word.
She's driven four hundred miles' distance to find the answer.
We've put six months' work into the project.
Last week's salary was paid on Friday.
Use with Abbreviations
When using an abbreviation, place the apostrophe directly after the final period of the abbreviation followed by an "s".
She spoke with the Ph.D.'s assistant.
Three Brother Inc.'s latest product is amazing!
Use with Compound Nouns
Follow the same rules for compound nouns as with other nouns.
My sister-in-law's job is very stressful.
Our human resource manager's reply should arrive next week.
Use to Express Plural Letters and Numbers
In some cases we use plural letters, symbols or numbers when giving telephone numbers, spelling, etc. In these cases, place an apostrophe after the letter, symbol or number followed by an "s".
Make sure to dot the i's and cross the t's on that document.
There are three 5's in the area code.
Use with Possession by Multiple People
Sometimes a number of individuals may be named as the owner of something. In this case, place the apostrophe after the final name followed by an "s".
Mary and Tom's house is down the street.
Smith, Peter, and Thompson's products are superb.
Use with Indefinite Pronouns
An apostrophe can also be used with an indefinite pronoun such as anybody and everybody followed by an apostrophe and an "s".
Who will win is anybody's guess.
Everyone's experience is important.
Apostrophe for Contraction of Verb Forms
One of the most common uses of apostrophes is to contract verb forms. Contractions are used for both positive and negative forms of the helping verb such as won't, isn't, I'd, etc.
He's a teacher at our school.
They aren't going to attend the show.
Apostrophe to Omit a Letter from a Word or Number
Finally, apostrophes are used to omit a letter or number such as dropping the first two digits of a year.
I'm part of the class of '79.