the dry, one-seeded fruit of any of various trees or shrubs, consisting of a kernel, often edible, in a hard and woody or tough and leathery shell, more or less separable from the seed itself, as the walnut, pecan, chestnut, acorn, etc.
the kernel, or meat, of such a fruit
loosely any hard-shell fruit that will keep more or less indefinitely, as a peanut, almond, etc.
a small block, usually of metal, with a threaded hole through the center, for screwing onto a bolt, screw, etc.
a ridge of ebony or other hard material at the top of the fingerboard of a stringed instrument, over which the strings pass
the small knob at the end of a violin bow, for tightening or loosening the hairs
Informal the initial cost of an undertaking, or the amount of money it is necessary to take in before a profit is realized on it