One of a pair of pointy projections, either straight, curved or helical, which have grown from the head of an animal. The animals that have horns include cows, sheep, goats, antelope, and their relatives. The rhinoceros is an exception because its single horn grows from its nasal bone. Deer grow antlers instead of horns. Antlers are made of bone, and go through annual cycles of growing out and shedding. "Horn" can also refer to a substance which is the outermost part of a horn ? tough keratin, a type of protein. It usually develops as a conical sheath over bone. Keratin also covers the hooves, claws, and nails of various animals, as well as armadillo and tortoise shells, the scales of the pangolin, porcupine quills, and birds' feathers. A rhinoceros horn is the only horn that is a solid growth of keratin. It also consists of some fused hair.Horn has been used as a medium in the production of combs, buttons, the handles of canes and knives, drinking-cups, spoons, snuff-boxes, and other objects.Trade in the horns of certain animals is unethical (sometimes illegal) often because its species is in danger of extinction. Antlers are more ethical to use in producing art, because antlers are naturally shed by deer (and related animals) annually, falling to the ground where they can be collected. Various plastics simulate horn quite well. Plastics might be considered a more moral alternative to horn or as an overly artificial substitute. Horn is comparable in some ways to ivory, teeth, bone, and shell; the use of any of which is also capable of generating ethical dilemmas. Wood, glass, and stone are among the other alternatives to horn.The unicorn is a mythological horse that projects one horn from its forehead.Devils, cuckholds, and various fantastic creatures are traditionally depicted as having horns.Hollow horns have been used as vessels. "Powderhorns" hold gunpowder, and were long made of horn. A cornucopia or "horn of plenty" is a goat's horn overflowing with fruit, flowers and grain. The legendary Greek nymph Amalthea's magical horn rewarded its possessor's every wish. Now the cornucopia is a symbol of abundance.In music, either an early instrument made of an animal's horn (e.g. see thumbnail to righta shofar), or a wind instrument made of brass and consisting of a long tube with a flared end that produces a sound when the player's lips vibrate together in the mouthpiece ? barritone horns, bugles, saxophones, French horns, tubas, Flugelhorns, trombones, cornettes, and trumpets.Any shape or form which resembles a horn, such as one of the curved ends of a crescent, a mountain peak, an erect penis, the beak-shaped part of an anvil, etc.