1.  shelf(n = noun.artifact) Array - a support that consists of a horizontal surface for holding objects; Array
is a kind of support
is a part of bookcase, buffet, counter, sideboard, cabinet, bureau, chest, chest of drawers, dresser, closet, etagere, food market, grocery, grocery store, market
has particulars: bookshelf, hob, chimneypiece, mantel, mantelpiece, mantle, mantlepiece, overmantel

2.  shelf(n = noun.object) ledge - a projecting ridge on a mountain or submerged under water; Array
is a kind of ridge
has particulars: berm
Derived form adjective shelfy₁

1.  A flat tablet or ledge of any material set horizontally at a distance from the floor, to hold objects of use or ornament. [1913 Webster]

2.  A sand bank in the sea, or a rock, or ledge of rocks, rendering the water shallow, and dangerous to ships. [1913 Webster]
"On the tawny sands and shelves." [1913 Webster]
"On the secret shelves with fury cast." [1913 Webster]

3.  A stratum lying in a very even manner; a flat, projecting layer of rock. [1913 Webster]

4.  A piece of timber running the whole length of a vessel inside the timberheads. D. Kemp. [1913 Webster]

shelf, n. (pl. shelves)
1 a a thin flat piece of wood or metal etc. projecting from a wall, or as part of a unit, used to support books etc. b a flat-topped recess in a wall etc. used for supporting objects.
2 a a projecting horizontal ledge in a cliff face etc. b a reef or sandbank under water. c = continental shelf.

Idiom:
on the shelf
1 (of a woman) past the age when she might expect to be married.
2 (esp. of a retired person) no longer active or of use. shelf-life the amount of time for which a stored item of food etc. remains usable. shelf-mark a notation on a book showing its place in a library. shelf-room available space on a shelf.

Derivative:
shelved adj. shelfful n. (pl. -fuls). shelflike adj.

shelf, n. & v. Austral. sl.
--n. an informer.
--v.tr. inform upon.

Etymology:
20th c.: orig. uncert.

N  pitfall, rocks, reefs, coral reef, sunken rocks, snags, sands, quicksands, syrt, syrtis, Goodwin sands, sandy foundation, slippery ground, breakers, shoals, shallows, bank, shelf, flat, lee shore, ironbound coast, rock ahead, breakers ahead, precipice, maelstrom, volcano, ambush, pitfall, trapdoor, trap, sword of Damocles, wolf at the door, snake in the grass, death in the pot, latency, ugly customer, dangerous person, le chat qui dort, firebrand, hornet's nest, latet anquis in herba, proximus ardet Ucalegon.

N  support, ground, foundation, base, basis, terra firma, bearing, fulcrum, bait, caudex crib, point d'appui, pou sto, purchase footing, hold, locus standi, landing place, landing stage, stage, platform, block, rest, resting place, groundwork, substratum, riprap, sustentation, subvention, floor, supporter, aid, prop, stand, anvil, fulciment, cue rest, jigger, monkey, stay, shore, skid, rib, truss, bandage, sleeper, stirrup, stilts, shoe, sole, heel, splint, lap, bar, rod, boom, sprit, outrigger, ratlings, staff, stick, crutch, alpenstock, baton, staddle, bourdon, cowlstaff, lathi, mahlstick, post, pillar, shaft, thill, column, pilaster, pediment, pedicle, pedestal, plinth, shank, leg, socle, zocle, buttress, jamb, mullion, abutment, baluster, banister, stanchion, balustrade, headstone, upright, door post, jamb, door jamb, frame, framework, scaffold, skeleton, beam, rafter, girder, lintel, joist, travis, trave, corner stone, summer, transom, rung, round, step, sill, angle rafter, hip rafter, cantilever, modillion, crown post, king post, vertebra, columella, backbone, keystone, axle, axletree, axis, arch, mainstay, trunnion, pivot, rowlock, peg, tiebeam, thole pin, board, ledge, shelf, hob, bracket, trevet, trivet, arbor, rack, mantel, mantle piece, mantleshelf, slab, console, counter, dresser, flange, corbel, table, trestle, shoulder, perch, horse, easel, desk, clotheshorse, hatrack, retable, teapoy, seat, throne, dais, divan, musnud, chair, bench, form, stool, sofa, settee, stall, arm chair, easy chair, elbow chair, rocking chair, couch, fauteuil, woolsack, ottoman, settle, squab, bench, aparejo, faldstool, horn, long chair, long sleeve chair, morris chair, lamba chauki, lamba kursi, saddle, pannel, pillion, side saddle, pack saddle, pommel, bed, berth, pallet, tester, crib, cot, hammock, shakedown, trucklebed, cradle, litter, stretcher, bedstead, four poster, French bed, bunk, kip, palang, bedding, bichhona, mattress, paillasse, pillow, bolster, mat, rug, cushion, footstool, hassock, tabouret, tripod, monopod, Atlas, Persides, Atlantes, Caryatides, Hercules, supporting, supported, fundamental, dorsigerous, astride on, straddle.

continental shelf, ice shelf, on the shelf, shelf bracket, shelf fungus, shelf ice, shelf life