Possessive apostrophe rules, with examples

A possessive apostrophe shows that something belongs to someone or something. For a singular noun, add an apostrophe and s: the student's essay. For a plural noun ending in s, add only an apostrophe: the students' essays. For a plural that does not end in s, add an apostrophe and s: the children's responses.

Those rules cover most of the apostrophes in an essay. The rest of this guide deals with the cases that cause genuine hesitation, from names ending in s to its and it's.

Possessive apostrophe rules at a glance

A reliable method is to write the owner first, in its correct singular or plural form, and only then add the apostrophe. If the word ends in s because it is plural, add an apostrophe alone. In every other case, add an apostrophe and s.

Check where the apostrophe goes after s

The apostrophe after s causes more hesitation than any other case, because the answer depends on why the word ends in s.

For names and singular nouns ending in s, both forms are accepted in British English. Most UK style guides, including New Hart's Rules from Oxford University Press, prefer adding 's because it matches the way the word is spoken. Classical names are a common exception, where many writers use the apostrophe alone, as in Socrates' argument. Choose one approach and use it every time.

Show joint and separate ownership

When two people own the same thing, put the apostrophe on the second name only. When each owns something separately, give both names an apostrophe.

This comes up often in literature reviews. A single co-authored paper takes one apostrophe, while two separate papers take one each. Our Harvard referencing guideshows how to cite multiple authors in the text itself.

Put the apostrophe at the end of a compound

With a compound noun or a title made of several words, the apostrophe goes at the end of the whole phrase, not on the main noun: the head of department's decision, or the Secretary of State's powers.

Academic writing uses possessives constantly with named theories and models, such as Maslow's hierarchy of needs or Porter's five forces. When the owner is a long organisation name, a phrase with of usually reads better. The recommendations of the World Health Organization is easier to follow than the World Health Organization's recommendations, and it avoids the apostrophe decision altogether.

Tell its and it's apart

Its and it's are the pair that most often survive into a final draft. The rule becomes simple once you know that possessive pronouns never take an apostrophe.

To test a sentence, replace the word with it is. If the result makes sense, you need it's. Hers, ours, yours, theirs and whose follow the same pattern as its, with no apostrophe. Contractions are usually avoided in formal academic writing, so in an essay you will rarely need it's at all.

Use apostrophes in time phrases

British English treats many time expressions as possessive. One week's notice, two weeks' notice and three years' experience all take apostrophes, following the same singular and plural rules as any other noun. These phrases turn up more in personal statements and CVs than in essays, which is where they are most often missed.

Leave apostrophes out of plurals

An apostrophe never makes a word plural. That applies to ordinary nouns, acronyms, numbers and decades alike.

An acronym needs an apostrophe only for possession, as in the NHS's workforce plan. Some organisations also drop apostrophes from their names by choice. Waterstones removed its apostrophe in 2012, while King's College London keeps its own, so check the official name before you write it.

Find apostrophe errors in a draft

Use your word processor's find function to search for 's and then for s'. For each result, ask who or what the owner is and whether it is singular or plural. Then search for it's on its own, because in an academic essay nearly every instance should be its or it is.

Do not rely on a grammar checker alone. Checkers handle its and it's reasonably well but often miss an apostrophe in the wrong place on a plural owner, because both versions are real words.

Apostrophes sit alongside commas as the punctuation errors markers notice most, and our guide towhen to use a comma covers the other half. For more mistakes that survive into final drafts, see common grammatical errors.

If you would rather have every apostrophe checked, our proofreaders correct punctuation across the whole document and show each change in tracked changes, so you can learn the pattern as you review them.

Last updated: 14 September 2026 · Written by the AssignWise editorial team ·Spotted something wrong?