Flat

Flat is a polysemous term in the English language with several unrelated senses across everyday language, housing, music, and everyday objects.

As an adjective, flat describes a surface that is level and even, lacking curves, bumps, or variation in height. It can refer to terrain, objects, or textures that are smooth and plane, and it can also describe tones or performances that are dull or lacking vibrancy.

As a noun, flat most commonly denotes a dwelling unit in British English, typically one apartment within a building. In American English, the equivalent term is apartment. Flats are usually rented, though they may also be owned, and they form an important element of urban housing stock.

In music, a flat is a symbol, ♭, used to indicate that a note should be lowered by one semitone. Flats appear in key signatures and accidentals and are essential for naming pitches such as A♭, B♭, or E♭. The concept contrasts with sharp and natural, and it plays a central role in Western tonal music.

In everyday usage, flat can describe beverages that have lost carbonation, such as flat soda. It is also used to describe a tire that has been punctured or has lost air, as in a flat tire.

The word exhibits diverse meanings that modern English speakers rely on, from describing surfaces and dwellings to signaling pitch in music and indicating a lack of carbonation or air.