A closet (especially in North American English usage) is an enclosed space, with a door, used for storage, particularly that of clothes. Fitted closets are built into the walls of the house so that they take up no apparent space in the room. Closets are often built under stairs, thereby using awkward space that would otherwise go unused.

A piece of furniture such as a cabinet or chest of drawers serves the same purpose of storage, but is not a closet, which is an architectural feature rather than a piece of furniture. A closet always has space for hanging, where a cupboard may consist only of shelves for folded garments. Wardrobe can refer to a free-standing piece of furniture (also known as an armoire), but according to the Oxford English Dictionary, a wardrobe can also be a "large cupboard or cabinet for storing clothes or other linen", including "built-in wardrobe, fitted wardrobe, walk-in wardrobe, etc."