An ape (family Hylobatidae) that is smaller than any of the great apes (chimpanzee, bonobo, gorilla, orangutan, and human), with long arms, long hands and feet, highly flexible wrists, and an extremely loud voice. Gibbons are social, territorial, and arboreal, moving mainly by brachiation. They feed mainly on fruit, augmented with other plant material and bird eggs. There are four genera with 17 species, found in Asian rainforests.