loft can be an upper storey or attic in a building, directly under the roof. Alternatively, a loft apartment refers to large adaptable open space, often converted for residential use (a converted loft) from some other use, often light industrial. Adding to the confusion, some converted lofts include upper open loft areas. Within certain upper loft areas exist even further lofts, which may contain loft areas of their own, and so forth.
An upper room or story in a building, mainly in a barn, directly under the roof, used either for storage (as in most private houses), for a specific purpose, e.g. an "organ loft" in a church, or to sleep in (sleeping loft). In this sense it is roughly synonymous with attic, the major difference being that an attic typically constitutes an entire floor of the building, while a loft covers only a few rooms, leaving one or more sides open to the lower floor. In barns a hayloft is often larger than the ground floor as it would contain a year's worth of hay.