Contractions are shortened forms of words and phrases, in which some letters or sounds are omitted. An apostrophe marks the omission. Most contractions in English combine two words to form a single shorter word—for example, do and not combine to form don’t. A contraction may also simply be a single word that is shortened, such as ma’am.

Standard contractions include those that shorten the word not (like don’t, isn’t, couldn’t), forms of the be verb (I’m, you’re, he’s), the have verb (I’ve, she’s, they’ve), and the modal verbs will and would (I’ll, he’ll, you’d). Two other common contractions are ma’am (for madam) and let’s (for let us).

At the end of this article is a full list of standard contractions in English, but here is a quick cheat sheet.

English also has other contracted forms, some of which are nonstandard and avoided in writing. For a full discussion, see Types of Contractions in English.

Forms of the be verb (is, am, are) often join with pronouns (such as I, you, she, they, someone) to form contractions.

The be verb can also join with nouns to form contractions. These are common in speech and informal writing but not seen in edited prose (except in dialogue in fiction) and never in formal writing.

Plural contractions are rarer still in writing (The cats’re asleep).

The be verb can also combine with adverbs to form contractions in speech and informal usage.

The be verb (is, are, am) contracts with not in two ways: you can either contract the verb form itself or contract not.

The word not is contracted more often with nouns.

But with pronouns, the verb form is contracted more often instead.

The have verb combines with pronouns and nouns and contracts to ’ve, ’s, or ’d.

The have verb is not contracted in writing when it is the main verb in a sentence and means “to possess.”

The modal verbs will and would contract to ’ll and ’d in casual communication.

The contracted form ’d can mean both would and had. Context makes it clear what you’re referring to.

Similarly, the contracted form ’s can represent both is and has.

Another interesting contraction is what’s, which can mean what is, what has, and even what does in informal usage.

Let’s is an exception in that it is a contraction of let us, not let is or let has (which options would be nonsensical anyway).

Negative forms using not are contracted in questions both in speech and formal usage.

Negative question tags are also always contracted.

Forms of be and have can combine with question words like who and what in speech.

Contractions of words like what, where, and there with the plural verb are (what’re, where’re, there’re) are less common than singular forms (what’s, where’s, there’s).

Don’t use affirmative contractions at the end of a sentence or a clause.

It’s fine to use negative contractions to end a sentence or a clause.

Contractions are common in speech and informal and creative writing, such as in dialogue.

Avoid using contractions in formal texts, such as cover letters, academic papers, and business reports, which require a more formal tone.

Both contractions and possessives may contain a noun followed by an apostrophe and s. An easy way to check is to try expanding the term: if you can expand it to two words, it’s a contraction; otherwise, it’s a possessive.

Possessive pronouns (like hers, theirs, its) never contain an apostrophe. If you have an apostrophe and s with a pronoun, it’s a contraction, not a possessive. For example, it’s (with the apostrophe) is a contraction of it is or it has, while its (without an apostrophe) is a possessive.

If you can expand it, it’s a contraction, not a possessive.

Here is a useful list of commonly used contractions in English.