big nail, clapper

I deepen

depth

(physics) fundamental interaction

fundamental, core / intrinsic / substantial

(physics) fundamental force

deep, profound, abstruse

a slice, portion

kernel (of nut), meat (of walnut) / core, pith, stone (of fruit) / clove (of garlic) / cotyledon / core, essence, heart

scrap of cloth (used for repairing or stuffing clothes or mattresses)