A set of rooms for living in, usually on one floor of a larger building. Used mainly in British English. The American English word is 'apartment'.

Countable noun. Plural: flats. Common collocations: studio flat (one room), flat-share (sharing a flat), ground floor flat, flat mate (someone you share a flat with). Note: 'flat' also means not curved or smooth (a flat surface).

In Britain, 'flat' is the standard word for an apartment. Many people in British cities live in flats rather than houses due to cost and availability. 'A flatmate' is the British term for a roommate — someone you share a flat with.