Apostrophe

from grammarbook.com

Rule 1: Contractions

Use the apostrophe with contractions. The apostrophe is always placed at the spot where the letter(s) has been removed.

Examples:

don't, isn't

You're right.

She's a great teacher.

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Rule 2: Possession

Use the apostrophe to show possession. Place the apostrophe before the s to show singular possession.

Examples:

one boy's hat

one woman's hat

one actress's hat

one child's hat

Ms. Chang's house

my mother-in-law's hat

NOTE: Although names ending in s or an s sound are not required to have the second sadded in possessive form, it is preferred.

Examples:

Mr. Jones's golf clubs

Texas's weather

Ms. Straus's daughter

Jose Sanchez's artwork

Dr. Hastings's appointment (name is Hastings)

Mrs. Lees's books (name is Lees)

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Rule 3: Implied Nouns

Use the apostrophe where the noun that should follow is implied.

Example:

This was his father's, not his, jacket.

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Rule 4: Plural Possession

To show plural possession, make the noun plural first. Then immediately use the apostrophe.

Examples:

two boys' hats two women's hats

two actresses' hats

two children's hats

the Changs' house

the Joneses' golf clubs

the Strauses' daughter

the Sanchezes' artwork

the Hastingses' appointment

the Leeses' books

Rule 5: Plural Names (NO APOSTROPHE)

Do not use an apostrophe for the plural of a name.

Examples:

We visited the Sanchezes in Los Angeles.

The Changs have two cats and a dog.

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Rule 6: Plural Compound Nouns

If the compound noun is plural, form the plural first and then use the apostrophe.

Example:

my two brothers-in-law's hats

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Rule 7: 2nd Name Only

Use the apostrophe and s after the second name only if two people possess the same item.

Examples:

Cesar and Maribel's home is constructed of redwood.

Cesar's and Maribel's job contracts will be renewed next year.

Indicates separate ownership.

Cesar and Maribel's job contracts will be renewed next year.

Indicates joint ownership of more than one contract.

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Rule 8: Possessive Pronouns (No Apostrophe)

Never use an apostrophe with possessive pronouns: his, hers, its, theirs, ours, yours, whose. They already show possession so they do not require an apostrophe.

Correct:

This book is hers, not yours.

Incorrect:

Sincerely your's.

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Rule 9: It's

The only time an apostrophe is used for it's is when it is a contraction for it is or it has.

Examples:

It's a nice day.

It's your right to refuse the invitation.

It's been great getting to know you.

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Rule 10: Capital Letters and Numbers

The plurals for capital letters and numbers used as nouns are not formed with apostrophes.

Examples:

She consulted with three M.D.s.

BUT

She went to three M.D.s' offices.

The apostrophe is needed here to show plural possessive.

She learned her ABCs.

the 1990s not the 1990's

the '90s or the mid-'70s not the '90's or the mid-'70's

She learned her times tables for 6s and 7s.

Exception:

Use apostrophes with capital letters and numbers when the meaning would be unclear otherwise.

Examples:

Please dot your i's.

You don't mean is.

Ted couldn't distinguish between his 6's and 0's.

You need to use the apostrophe to indicate the plural of zero or it will look like the word Os. To be consistent within a sentence, you would also use the apostrophe to indicate the plural of6's.

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Rule 12: Possessive in front of 'ing'

Use the possessive case in front of a gerund (-ing word).

Examples:

Alex's skating was a joy to behold.

This does not stop Joan's inspecting of our facilities next Thursday.

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Rule 13: 

If the gerund has a pronoun in front of it, use the possessive form of that pronoun.

Examples:

I appreciate your inviting me to dinner. I appreciated his working with me to resolve the conflict.