Both terms refer to a personal residence consisting of a series of rooms located on the same floor, within a larger, singular building. Below we discuss the main differences between an apartment, a condo a loft and a flat. The greatest difference is that the word “apartment” is more commonly used in American English, whereas the term “flat… Flat is a synonym of apartment. Flat is used in British English, and apartment is used in North American English. Although granted, there is a little difference between one and the other, architects, real estate brokers, contractors and land developers would tell you different. But when I lived in England a few years back, a friend of mine would always giggle when I said "apartment" -- when I finally asked her why, she said that "apartment" applied only to veddy veddy posh flats occupied by Sloane Rangers and the like. As a adjective flat is having no variations in height. Apartment vs Flat. Both words refer to a residential unit rented out to tenants. The exact meaning of the word apartment depends on where you live.. If you’d like to get a little more technical (why not), the British flat refers to a humble, ordinary residence. There is no physical difference between an apartment and a condo. What, then, is the difference between an apartment and a flat? As a adverb flat is so as to be flat. Generally speaking, there is no difference between an apartment and a flat. As nouns the difference between flat and apartment is that flat is an area of level ground or flat can be (chiefly|british) an apartment while apartment is a complete domicile occupying only part of a building. As an American, I'd never considered there was any difference beyond "flat" being the preferred word in British English. In large parts of Canada and in or near New York City, it is used for a residence in a multi-unit building; this meaning is the one given by OALD, and is a synonym of the British word flat..