Key Difference: The primary difference between an apartment and a flat is that the term ‘apartment’ is mostly used in American English, whereas ‘flat’ is used in UK or British English. Both indicate a set of rooms that are on the same floor and are meant to be used as a personal residence.

Though it is rare, there often comes along a time where two words mean the same thing though they are often used by different people differently. Two such terms are ‘apartment’ and ‘flat.’ Both of these terms mean the same thing, or more accurately have a similar definition. They primarily define a set of rooms that are used for individual residence, i.e. living in.

However, the actual implication of what an apartment or a flat define may differ from region to region, as in the UK, an apartment can be a set of rooms set within a house. Whereas, in other parts of the world, such as the USA, the terms may indicate a condo, i.e. individual living spaces in a building.

As indicated, the primary difference between an apartment and a flat is that the term ‘apartment’ is mostly used in American English, whereas ‘flat’ is used in UK or British English. However, due to globalization, both of these terms are now commonly being used interchangeable around the world.