B1 Grammar Nouns

Compound Nouns: Open, Hyphenated and Closed Forms

A compound noun is two or more words working together as a single noun — written as separate words (bus stop), with a hyphen (mother-in-law), or joined into one (toothbrush).

A compound noun is a noun made of two or more words that function together as a single unit of meaning. The parts may be written as separate words (bus stop), linked with a hyphen (mother-in-law), or joined into one solid word (toothbrush). Whatever the spelling, the whole compound behaves like one noun: it has a single meaning and takes a single plural.

Compound nouns are everywhere in everyday British English — from washing machine and swimming pool to haircut and traffic light. Learning how they are formed, where the stress falls, and how they make their plurals will help you sound natural and avoid common spelling and grammar errors.

The Three Written Forms

There is no single rule for when a compound is spaced, hyphenated or solid — spelling often settles over time as a word becomes more common. When in doubt, check a good British dictionary such as Oxford or Cambridge.

Form Description Examples
Open / spaced written as two or more separate words bus stop, swimming pool, post office
Hyphenated joined by one or more hyphens mother-in-law, check-in, self-control
Closed / solid written as a single joined word toothbrush, haircut, football

Spelling tip: The same idea can change form over time. Many compounds begin as two words, become hyphenated, then finally close up — for example to-day became today, and e-mail is now usually written email. If you are unsure, follow the spelling in a current British dictionary.

How Compound Nouns Are Formed

Compound nouns are built from different combinations of word classes. By far the most common pattern is noun + noun, but several others are frequent too.

Structure Examples
noun + noun bus stop, toothbrush, football, postman
adjective + noun greenhouse, blackboard, software
verb + noun breakfast, pickpocket, washing line
gerund (-ing) + noun swimming pool, washing machine, frying pan
noun + verb haircut, sunrise, rainfall
preposition / particle + noun onlooker, bystander, underworld
verb + preposition check-in, make-up, workout

In nearly every case, the second element is the head — it tells you what kind of thing the compound is. A toothbrush is a kind of brush; a bus stop is a kind of stop. The first element modifies the head, telling you what it is for or what type it is.

Stress in Compound Nouns

Stress is one of the clearest signals of a true compound noun. In most compound nouns, the main stress falls on the first element. This often distinguishes a compound noun from an ordinary adjective + noun phrase, where the stress is more even or on the second word.

Listen for the stress: If the stress is firmly on the first word, you are almost certainly hearing a fixed compound noun with a special meaning. If the two words have roughly equal stress, you are probably hearing an ordinary adjective describing a noun.

Compound Noun or Adjective + Noun Phrase?

It is easy to confuse a compound noun with an ordinary adjective + noun phrase. A compound noun names a single, fixed type of thing, while an adjective + noun phrase simply describes a noun. Compare:

A useful test: in a compound noun you usually cannot add another adjective between the two parts, and you cannot grade the first element with very. We do not say a very greenhouse or a green big house with the compound meaning.

Making Compound Nouns Plural

For most compound nouns, you simply add the plural ending to the last word. But with hyphenated compounds, the plural usually goes on the most important word (the head), which may not be the last one.

Rule Singular Plural
Add -s to the last word (most compounds) toothbrush toothbrushes
Add -s to the last word bus stop bus stops
Pluralise the head noun, not the last word mother-in-law mothers-in-law
Pluralise the head noun, not the last word passer-by passers-by
Pluralise the head noun (military / legal style) court-martial courts-martial
Compounds with no clear noun add -s at the end grown-up grown-ups

So we say two bus stops and three toothbrushes, but my two mothers-in-law and several passers-by, because mother and passer are the real nouns being counted.

Compound Nouns and Possession

When the first noun simply describes the type or purpose of the second, we use a plain compound noun, not a possessive. A bus stop is a stop for buses, so we do not write bus’s stop. Use the apostrophe only for genuine possession.

Common Mistakes

Practice Exercises

Grammar Quiz

Choose the correct form and plural of each compound noun.

Matching Pairs

Match the two halves to build natural compound nouns.

Cloze Dropdown

Select the right compound noun to complete each sentence.

Flash Cards

Drill common compound nouns and their meanings.

Complete the Sentence

Type the correct compound noun or its plural to finish each sentence.

Unjumble

Reorder scrambled words into sentences using compound nouns.

Practise Compound Nouns

LexFizz has 30 free interactive exercises — no sign-up needed. Start mastering compound nouns and their plurals today.

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Frequently Asked Questions

What is a compound noun?
A compound noun is a noun made of two or more words that work together as a single unit of meaning, such as bus stop, mother-in-law or toothbrush. The whole compound behaves like one noun: it has one meaning and takes one plural. The second part is usually the head, telling you what kind of thing it is, while the first part says what type or purpose it has.
What are the three forms of compound nouns?
Compound nouns are written in three ways. Open or spaced compounds are two separate words, such as bus stop and swimming pool. Hyphenated compounds are joined by a hyphen, such as mother-in-law and check-in. Closed or solid compounds are written as one word, such as toothbrush and football. There is no fixed rule, so check a current British dictionary when unsure.
How are compound nouns formed?
Compound nouns are built from different word classes. The commonest pattern is noun + noun (toothbrush, bus stop), but you also find adjective + noun (greenhouse), verb + noun (breakfast), gerund + noun (swimming pool), noun + verb (haircut) and verb + preposition (check-in). Whatever the parts, the result is a single noun with its own meaning.
Where does the stress fall in a compound noun?
In most compound nouns the main stress falls on the first element, as in GREENhouse, BLACKbird and BUS stop. This is one of the clearest signs of a true compound. An ordinary adjective + noun phrase, by contrast, usually has more even stress or stress on the second word, as in a green HOUSE meaning a house that is green.
How do you make compound nouns plural?
For most compound nouns you add the plural ending to the last word: toothbrush becomes toothbrushes and bus stop becomes bus stops. With many hyphenated compounds, however, you pluralise the most important word, which may not be the last one: mother-in-law becomes mothers-in-law and passer-by becomes passers-by.
Is it ‘mother-in-laws’ or ‘mothers-in-law’?
The correct plural is mothers-in-law. The plural ending goes on the head noun, mother, because that is the word being counted — you have several mothers who are linked to you in law. The same logic gives passers-by and courts-martial. Writing mother-in-laws is a very common mistake but it is not standard.
What is the difference between a compound noun and an adjective + noun phrase?
A compound noun names a single, fixed type of thing, while an adjective + noun phrase simply describes a noun. A greenhouse is a structure for growing plants, not just a green house. Compound nouns usually carry the stress on the first word and you cannot insert another adjective between the parts or grade the first part with very.
Should I use an apostrophe in compound nouns like ‘bus stop’?
No. When the first noun describes the type or purpose of the second, you use a plain compound noun with no apostrophe. A bus stop is a stop for buses, so you write bus stop, not bus’s stop; likewise car door and teacup. Use the apostrophe only for genuine possession, as in the teacher’s book.
Why is the first noun usually singular in a compound noun?
When a noun is used to modify another noun, it normally stays singular even when the meaning is plural. We say a shoe shop (a shop that sells shoes), not a shoes shop, and a toothbrush, not a teethbrush. The first noun works almost like an adjective, so it does not take a plural ending. A few fixed exceptions exist, such as sports car and arms race.
At what level should I learn compound nouns?
Basic compound nouns appear from B1 (intermediate) on the CEFR scale, where learners meet everyday examples such as bus stop and swimming pool. The finer points — choosing the right written form, hearing the stress, and forming irregular plurals such as passers-by — are usually mastered at B2 and C1, and they help your writing and speech sound natural and accurate.