Written by tutor Trisha P.
What is an apostrophe?
The apostrophe is a punctuation mark.
How an Apostrophe Is Used
The apostrophe is used for three purposes:
- To show possession or ownership
- To indicate the omission of letters
- To show the plural form or possessive of some letters and numbers
Now, let’s look at each use in greater detail.
Possessive or Ownership
First, you need to decide if you need a possessive. Remember the possessive form is used to show ownership. To test for the need for a possessive, use the prepositional phrase "of the ..." in place of the possessive. For example, “the student’s book” can be written as “the book of the student.” This shows that a possessive is appropriate.
Once you have determined that a possessive is needed, use the following rules to form the possessive:
|Base Word||To form the possessive||Examples|
|Singular||Add 's at the end of the word.||the boy's sports equipment
Mrs. Jones's car
Note: the 's is the preferred form of the possessive,
although Jones' car (no s) is acceptable.
|Singular compound noun||Add 's at the end of the compound.||my sister-in-law's friend|
|Singular noun implied||Add 's where the noun that
should follow is implied.
|That was my sister's, not my, chore.
Note: In this example, chore is implied after sister (i.e., my sister's chore).
|Plural ending in s||Add ' after the s.||the two girls' backpacks
the Joneses' swimming pool
Note: Joneses is the plural form of a family whose last name is Jones.
|Plural not ending in s||Add 's after the plural form of the word.||the children's teacher
the deer's antlers
|Plural compound noun||Form the plural, then use 's at the end of the compound.||my sisters-in-law's friends
Note: The plural of the compound is made by adding an s to sister. The compound plural does not end in s, so add 's after "law."
|Compound - separate ownership||Add 's after each part of the compound.||Alex's and Cathy's apartments are located in the same village.
Note: Alex and Cathy each have an apartment.
|Compound - joint ownership||Add 's after the second word (usually a name) only.||Alex and Cathy's apartment is located six blocks from school.
Note: Alex and Cathy share an apartment.
|Gerunds (-ing words used as nouns)||Use the possessive form in front of the gerund.||Theresa's piano playing is phenomenal.
Note: "Playing" is a gerund, not a verb, in this sentence.
I appreciate your inviting me to dinner.
Note: "Inviting" is a gerund; "your" is the possessive pronoun.
Do not use apostrophes with:
- The plural of a name (e.g., The Carrolls are visiting friends in five states. Carrolls is the plural of the last name Carroll.)
- Possessive pronouns (e.g., This package is theirs, not ours. Theirs and ours are possessive pronouns.)
The Omission of Letters (Contractions)
A second use of the apostrophe is to communicate the omission of letters. These shortened words are called contractions. The apostrophe is placed where the letter(s) has been removed.
Examples: it is = it’s do not = don’t
Note: The apostrophe is often misplaced with “its” because the word is both a possessive pronoun and a contraction. To ensure that you have used the apostrophe correctly, ask yourself if you can change “its” to “it is” in the sentence. If you can, then an apostrophe after the “t” is correct. If you cannot, then you are using “its” as a possessive pronoun and no apostrophe is used.
Letters and Numbers: Plurals and Possessives
Sometimes an apostrophe is used for plurals or possessives of letters and numbers.
The basic rule is to use an apostrophe in only two instances:
- To show the plural possessive and
- When the meaning would be unclear without the apostrophe.
She made appointments at three M.D.’s offices. An apostrophe is needed to show the plural (i.e., three different offices, not three doctors in a single office).
Bethie worked for three M.D.s. No apostrophe is needed as this is simply the plural form of M.D., not a plural possessive.
The teacher often told her students to be sure to dot their i’s and cross their t’s. It was her way of saying that the students should pay attention to detail. An apostrophe is needed with “i” so that the word “i’s” is not confused with “is.” The apostrophe is used with “t” for consistency within the sentence. If you had written only “Cross your ts,” an apostrophe would not be needed.
Apostrophe Practice Quiz
Try out your new understanding of apostrophes with the following sentences. Read the sentence and decide if it is correct as written. If the sentence is correct, do nothing. If the sentence is not correct, make the necessary corrections. The answers follow the five sentences.
The teacher told the students to end their letters with the complimentary close, “Sincerely your’s.”
The teacher told the student to end their letters with the complimentary close, "Sincerely yours." "Yours" is a possessive pronoun; no apostrophe is needed.
Stephen’s 6’s and O’s looked the same.
The apostrophe after the O is needed so the word is not confused with Os. For consistency within the sentence, an apostrophe is used with 6 as well.
My mother asked me to stop at the Jones house on the way home to pick up the groceries Mrs. Jones’ had bought.
My mother asked me to stop at the Joneses’ house on the way home to pick up the groceries Mrs. Jones had bought. Joneses is the plural of Jones. An apostrophe is needed after the final s to show possession (i.e., the Joneses own the house). An apostrophe is not needed with Mrs. Jones because there is no ownership.
Let’s see if the dog has found its bone.
Correct as written. “Its” is the possessive pronoun.
My brother’s-in-law’s car was stolen from its parking place.
My brother-in-law’s car was stolen from its parking place. Brother-in-law is a compound word. The possessive is formed by adding ‘s at the end of the last word. The possessive form is needed because the car belongs to the brother-in-law.