Compound nouns
A compound noun is a noun made by joining two or more words together to create one new meaning, for example "toothbrush", "mother-in-law" or "swimming pool". The words can be written as one word, separate words, or joined with a hyphen. Compound nouns often combine noun+noun, adjective+noun, or verb+noun to name a single thing, person, place or idea.
Types of compound nouns
Closed (solid) compound nouns
Two words joined together with no space to form one single word.
e.g. toothpaste, notebook, haircut
Open (spaced) compound nouns
Two or more separate words that function together as one noun.
e.g. swimming pool, credit card, bus stop
Hyphenated compound nouns
Words joined by a hyphen, often to avoid confusion or awkward spelling.
e.g. mother-in-law, check-in, well-being
Noun + noun compounds
Two nouns combined where the first noun describes or limits the second.
e.g. football, keyboard, car park
Verb/gerund + noun compounds
A verb or -ing form combined with a noun to describe purpose or function.
e.g. washing machine, driving licence, swimming pool
Rules to remember
- Compound nouns can be written as one word, two words, or with a hyphen; there is no single fixed rule, so it is best to check a dictionary for the accepted form.
- The main stress usually falls on the first word when spoken, for example 'GREENhouse' (a building) versus 'green HOUSE' (a house that is green).
- To make a compound noun plural, usually only the final word changes, for example 'toothbrushes', 'bus stops'; but in compounds with 'in-law' or similar, the main noun changes, for example 'mothers-in-law'.
- The meaning of a compound noun is often not simply the sum of its parts; it names a specific new thing, for example a 'greenhouse' is not just a house that is green.
- Compound nouns commonly combine noun+noun, adjective+noun, verb+noun or gerund+noun, and the first word usually functions like an adjective, describing the second.
Examples in sentences
| Example | How it works |
|---|---|
| She bought a new toothbrush and some toothpaste this morning. | 'Toothbrush' and 'toothpaste' are closed compound nouns written as one word. |
| We are meeting at the bus stop near the swimming pool. | 'Bus stop' and 'swimming pool' are open compound nouns written as separate words. |
| My mother-in-law is visiting us for the check-in at the hotel. | 'Mother-in-law' and 'check-in' are hyphenated compound nouns. |
| He left his driving licence in the washing machine. | Both compound nouns use a verb/gerund form combined with a noun. |
| There are two mothers-in-law coming to the wedding. | Shows correct pluralisation: the main noun 'mother' changes, not 'law'. |
| The greenhouse at the back of the garden grows tomatoes all year. | Shows stress on the first word, distinguishing the compound noun from a literal 'green house'. |
| I need a new credit card because mine has expired. | 'Credit card' is an open compound noun formed from noun + noun. |
Common mistakes
Incorrect: I bought a new tooth brush.
Correct: I bought a new toothbrush.
Incorrect: There were three mother-in-laws at the party.
Correct: There were three mothers-in-law at the party.
Incorrect: She has a swimmingpool in her garden.
Correct: She has a swimming pool in her garden.
Why this matters for IELTS
Using compound nouns accurately and naturally (such as "traffic jam", "job satisfaction" or "part-time job") signals a wide, precise vocabulary and helps meet the Lexical Resource and Grammatical Range and Accuracy criteria in IELTS Writing and Speaking. Since spelling and pluralisation of compound nouns are irregular, learning the correct written form of common topic-related compounds (education, work, environment) in advance reduces small but noticeable errors that examiners may penalise.
Frequently asked questions
What is a compound noun?
A compound noun is a noun formed from two or more words combined to express one specific meaning, such as 'toothbrush', 'bus stop' or 'mother-in-law'. It can be written as one word, two separate words, or joined by a hyphen.
How do you make a compound noun plural?
Usually you make only the last word plural, for example 'toothbrushes' or 'bus stops'. However, in compounds like 'mother-in-law', the main noun changes instead, giving 'mothers-in-law'.
How do you know if a compound noun is one word, two words, or hyphenated?
There is no fixed rule; usage varies and changes over time. The safest method is to check a reliable dictionary for the currently accepted spelling of that specific compound noun.
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