The word flat has several, mostly unrelated uses:
- flat is a musical symbol representing a slightly lower pitch
- flatness
- A punctured tire is a "flat tire" or just a "flat"
- A flat tax charges the same percentage regardless of the size of the sum being taxed
- "flatline" is sometimes used as a synonym for death, describing the shape of an ECG graph with no heartbeat.
- A flat is another name for an apartment
- A tower block, block of flats, or apartment block is (in the 21st century) usually a high-rise apartment building.
- In New Zealand, flats refer to houses or other accommodation where groups of people, often University students, live together.
- Buildings containing low numbers of flats or apartments, or which are low-rise buildings such as tenement buildings, are described in the article on apartment buildings.
- In farming terms, "flats" may refer to valley floors where rich grazing is available when the steeper land is too bare.
- In abstract algebra, a module is flat if taking the tensor product with it preserves exact sequences.
- In computer programming, a flat memory model is an approach to organizing memory address space. Similarly, a flat file can refer to a flat file database or to a simple type of file system for computers.
