Compound Nouns Quiz
12 multiple-choice questions on English compound nouns: open, hyphenated and closed forms, plurals and stress. B1–B2 level.
Compound Nouns — FAQ
A compound noun is a noun made up of two or more words that work together as a single unit of meaning, such as 'toothbrush', 'bus stop' or 'mother-in-law'. The first part usually describes or modifies the second, so a 'swimming pool' is a pool used for swimming. Compound nouns let English build precise new words from existing ones, and they behave grammatically as one noun even when they are written as separate words.
English writes compound nouns in three forms: open (two separate words, like 'bus stop' or 'post office'), hyphenated (joined by a hyphen, like 'mother-in-law' or 'T-shirt'), and closed (written as one word, like 'toothbrush' or 'blackboard'). There is no single rule that decides the form, and usage can change over time as compounds become more familiar. When you are unsure, the safest approach is to check a current British dictionary for the accepted spelling.
For most closed and many open compounds, you add the plural ending to the final word, so 'toothbrush' becomes 'toothbrushes' and 'bus stop' becomes 'bus stops'. For hyphenated compounds, the plural normally goes on the most important (head) word, which gives 'passers-by' and 'mothers-in-law' rather than 'passer-bys'. A few compounds have irregular plurals because the main word is irregular, so always identify the head noun first.
In most two-word compound nouns, the main stress falls on the first word, so we say a GREENhouse, a BLACKboard and a SWIMming pool. This pattern helps listeners tell a compound noun apart from an ordinary adjective and noun, where the stress usually falls on the second word, as in a green HOUSE. Getting the stress right makes your spoken English clearer and more natural, especially for ESL learners.
A compound noun names a single thing or idea, while an adjective + noun simply describes a noun with a separate quality. A 'greenhouse' is one fixed thing (a glass building for growing plants), whereas 'a green house' is any house that happens to be green. The clearest test is meaning combined with stress: compound nouns are stressed on the first word and cannot usually be broken up by another word, while adjective + noun phrases can.
You use a hyphen mainly to join compounds that are not yet written as one word but need to be read as a single unit, such as 'mother-in-law', 'passer-by' and 'T-shirt'. Hyphens are also common when leaving the words separate would be confusing or ambiguous. Because British and American usage can differ, and because compounds drift from open to hyphenated to closed over time, it is wise to confirm the current spelling in a dictionary.
Yes, compound nouns are built from several word classes, not just two nouns. Many combine a verb or verb form with a noun, as in 'swimming pool', 'washing machine' and 'breakfast', while others include prepositions or particles, as in 'passer-by', 'check-in' and 'breakdown'. The grammatical job of each part can vary, but the whole combination always behaves as a single noun in a sentence.
For a hyphenated compound noun, you add the apostrophe and 's' to the end of the whole compound, so the possessive of 'mother-in-law' is 'mother-in-law's' and of 'brother-in-law' is 'brother-in-law's'. This is different from forming the plural, where the ending goes on the head word ('mothers-in-law'). If you need a plural possessive, English usually rephrases the sentence, because forms like 'mothers-in-law's' sound awkward.
'A blackbird' is a closed compound noun naming one particular species of bird, and it is stressed on the first syllable, BLACKbird. 'A black bird' is simply an adjective and a noun describing any bird that is black in colour, with the stress on BIRD. The spelling and stress together signal whether you mean the specific creature or just a bird of that colour, which is why pronunciation matters as much as the written form.
The most reliable method is to check a current British dictionary, since there is no rule that predicts every spelling and usage shifts over time. Reading widely and noticing how compounds are written in good-quality texts also builds your instinct, as does keeping a personal list of tricky examples. Practising with quizzes, flash cards and exercises helps fix the open, hyphenated and closed forms in your memory.