Noun shelf has 2 senses
  1. shelf - a support that consists of a horizontal surface for holding objects
    --1 is a kind of
    --1 is a part of
     bookcase; buffet, counter, sideboard; cabinet; closet; chest of drawers, chest, bureau, dresser; etagere; grocery store, grocery, food market, market
    --1 has particulars:
     bookshelf; hob; mantel, mantelpiece, mantle, mantlepiece, chimneypiece; overmantel
  2. ledge, shelf - a projecting ridge on a mountain or submerged under water
    --2 is a kind of ridge
    --2 has particulars: berm