shelf (noun) /ʃɛlf/
1
A flat, rigid structure, fixed at right angles to a wall or forming a part of a cabinet, desk etc., and used to support, store or display objects.
2
The capacity of such an object
3
A projecting ledge that resembles such an object.
4
(computing) The part of a repository where shelvesets are stored.
5
A reef, shoal or sandbar.