Lots of stories in here. | PATSTOCK/GettyImages

In the market for a house? You might tell your realtor you want atwo-story home. Headed for your job downtown? Your office might be in a five-story commercial building.

*Story *has long been a synonym for “floor,” or the level of a building. It often seems like we use story when on the exterior (“that building must be 20 stories tall”) and floor when inside (“we’re on the fourth floor”). But why use story instead of floor at all?

Why Building Floors Are Called “Stories”

According to the Oxford English Dictionary, the use of story in the context of a level of living quarters dates back to the 1300s. The most likely etymology is that story was taken from the Latin word historia, which once meant “history” but later came to mean “picture.” When denizens of the Middle Ages began decorating windows with paintings and illustrations, some of which may have told a sequential story across horizontal panes of glass, they collectively displayed a picture, or story. That eventually gave way to referring to the floor itself as a story.

It should be noted that Medieval homeowners were not quite fodder for Architectural Digest. Thatch-roofed huts with openings carved out were the norm. Windows and their accompanying decorations were usually found in churches or in the quarters of the well-to-do royals. The stained-glass religious iconography of churches lends further credence to this origin.

Another, less plausible explanation is that story came from the Gaelic word staidhir, or “flight of stairs.” Or perhaps story came from the Old French estoree, meaning “built thing.” Given the archaic origins, it’s been difficult for linguists to back any one source with confidence.

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Story vs. Feet

Story (spelled in the UK as storey) typically refers to a single floor of a building, or what the OED describes as “each of the sections of a building comprising all the rooms that are on the same level…the room or set of rooms which comprise one such level.”

Technically speaking, a story doesn’t need to be any particular size or configuration. One could erect an extremely narrow building and, so long as it has a separation of floors, each would be considered a single story. Nor does a story (floor) need to be exclusive. A condominium building may have several dwellings in one story.

There’s also not any kind of mandatory height. Residential buildings usually have about 10 feet of vertical space per story; commercial buildings might have up to 15 feet to accommodate more functional components (HVAC, plumbing, etc.). Regardless of ceiling height, each level is a story.

While story and floor are usually interchangeable, they don’t always mesh. A towering building might have a ground floor, but we don’t call it the “ground story.” A hotel guest might request a room on the top floor, but not the top story. And in the case of basements, any underground level is usually just that—underground, neither floor nor story. Real estate listings, for example, don’t usually count basement square footage when referring to the size of a home. But a finished attic? Well, that’s another story.

This article was originally published on mentalfloss.com as Why Do We Call Building Floors “Stories”?.