a flat piece of wood, metal etc fastened to a wall or in a cupboard, used to stand things on
jutting, flat area or piece
Cases of word usage
1) a support on a wall for a shelf etc (bracket)
2) a narrow shelf coming out from a wall, cliff, rock or other upright surface (ledge)
3) a shelf above a fireplace (mantelpiece)
4) to hang, project, over (something) like a shelf (overhang)
5) a framework with bars, pegs etc used for holding things, hanging things on etc; a shelf over the seats of a train, bus etc for light luggage (rack)
6) of shelf (shelves)
7) a flat shelf at the base of a window (sill)