Noun Plurals (UK)

You've just written "two mouses" in a story, and your teacher has put a neat circle round it. Or you've typed "three sister's" in a text and can feel something's not quite right, though you couldn't say what. Then there's sheep — is it sheeps when there's more than one? It sounds wrong, but so does leaving it the same.

Nobody's born knowing this. English plurals look simple for about thirty seconds — add an "s," done — and then real words turn up that break the pattern. It's not that you're bad at spelling; English plurals are several different systems layered on top of each other, borrowed from different languages, and once you can see the layers, the whole thing stops feeling random. This picks up where our piece on nouns leaves off. It's the UK English edition; American spelling differs slightly, and you'll find that in the US edition of this article.

The basic rules

Most nouns make their plural by adding -s — no drama: book → books, window → windows. Try -s first: if someone invented zorp tomorrow, you'd write zorps without thinking.

Some words can't take a plain -s because it would be awkward to say — try "bus-s." So English adds -es to nouns ending in -s, -ss, -sh, -ch, -x, -z: bus → buses, kiss → kisses, brush → brushes, church → churches, box → boxes, quiz → quizzes.

Nouns ending in -o are messier. Some take -es (potato → potatoes, hero → heroes); others, often newer or shortened words, take -s (photo → photos, piano → pianos). No single rule predicts every case, so a quick dictionary check is completely fair.

Nouns ending in -y depend on the letter before the y. Consonant + y → change y to i and add -es: baby → babies, story → stories. Vowel + y → just add -s: boy → boys, key → keys. That's why toy becomes toys but lady becomes ladies.

And a small but important habit: never use an apostrophe to make a plural. Three apple's is wrong; three apples is right. Apostrophes mark possession or missing letters — a different job entirely.

Common Mistake: Writing buss or boxs in a hurry. If a word already ends in a hissing sound, check whether it needs -es.

Spelling changes and irregulars

Nouns ending in -f or -fe. Some change to -ves: leaf → leaves, wolf → wolves, life → lives, wife → wives, shelf → shelves. But not all — some just add -s (roof → roofs, belief → beliefs, chief → chiefs), and a few allow both (scarf → scarfs or scarves). Learn the common -ves ones, and don't turn every -f into -ves (cliffs, not clivves).

The big irregular plurals. Some very common nouns keep patterns from a much older stage of English, and you just learn them as vocabulary:

man → men · woman → women · child → children · person → people · foot → feet · tooth → teeth · mouse → mice · goose → geese

You can't "work out" children from child the way you work out books from book. You meet them, you practise them, and they become automatic.

Nouns that don't change at all. Some have one form for both singular and plural — a number or verb shows which you mean: one sheep → two sheep, one fish → ten fish, one deer → several deer. More formal ones turn up in textbooks: series, species, aircraft. Watch series especially — it already ends in s. One series, two series. Never serieses.

Plural-only nouns only exist in the plural, usually because they describe things made of two joined parts: trousers, shorts, scissors, glasses, binoculars, pyjamas. They take plural verbs: My trousers are too long. For just one, use "a pair of": a pair of scissors.

Pro-Tip: If a letter before y confuses you, cover the y with your finger. If what's left ends in a, e, i, o, or u, you're safe with a plain -s.

The trickier corners

Compound nouns. A compound noun is two or more words used together as one: toothbrush, passer-by, sister-in-law. Usually you make the main noun plural, and often that's the last word: school buses, apple trees. But when the main noun comes first, you pluralise that: passers-by, mothers-in-law, runners-up, editors-in-chief.

Latin and Greek plurals. In science and history you'll meet nouns borrowed from Latin and Greek, often with two possible plurals — a "classical" one and a simpler -s one:

For criterion and phenomenon, the classical plural is strongly preferred — don't write criterions; for cactus and formula, both are genuinely in use. One trap: criteria is already plural, so "a criteria" is a howler — the singular is criterion.

Some nouns can't be counted at all and don't take a normal plural: information, advice, furniture, homework. You don't say informations; you use a "container" word — two pieces of information. There's much more in countable vs uncountable nouns.

Style. Sometimes an old plural sits where a simple -s is perfectly fine: stadiums rather than stadia; indexes for books, but indices in maths. Don't assume the "Latin" plural is always more correct — the sign of mastery isn't the fanciest plural, it's the right one for the subject and audience.

UK vs US Note

This is the UK English edition. Most plural rules are identical across UK and US English — the same irregulars, the same y→ies pattern — but a few words differ: British English talks about a building's storeys where American English uses stories for the same thing. If you also write in American English, the US edition covers those word-level differences; it's best not to mix the two systems in one piece of writing.

Quick check

1. Write the plural of each noun: a) box b) lady c) leaf d) child e) sheep

2. Choose the correct form in each sentence: a) The (mouses / mice) ran back into their hole. b) These (scissor / scissors) are very sharp. c) Two (passer-bys / passers-by) stopped to listen.

3. Fill in the gaps with the correct plural form: a) I've lost my ___________ (key). b) Three ___________ (woman) walked into the shop. c) We saw several different ___________ (species) of bird.

4. Which of these nouns do not normally change in the plural? a) series b) table c) fish d) trouser

5. For each word, write one correct plural. If there are two, just pick one. a) phenomenon b) cactus c) tooth d) mother-in-law

Where next

• What Is a Noun? — the Pillar 1 foundation this builds on.
• Countable and Uncountable Nouns (for why some words don't take a normal plural at all)
• Singular and Plural Agreement (for how plurals affect verb choice)
• UK vs US Plurals Compared (for cross-Atlantic differences in forms like storeys/stories)
• The US English edition of this article (for readers also working in American English)