A horn is a hard, pointed structure that can be found on the heads of various animals, such as cows, goats, and rhinos. It is made of keratin, the same protein that forms human hair and nails. Horns can serve multiple purposes, including defense against predators, competition for mates, and social signaling among members of the same species. In addition to animal horns, the term can also refer to musical instruments, like the French horn or trumpet. These instruments produce sound by vibrating air within a tube, often made of metal. Horns in music are used in orchestras and bands to create rich, melodic sounds.