A rodent (family Sciuridae) that is active by day, has a fully haired and often bushy tail, large ears and eyes, and four digits on the forelimbs and five on the hindlimbs, all with sharp claws. Most species are arboreal, but some are terrestrial or burrowing. There are about 58 genera of 285 species, native to Eurasia, Africa, and the Americas, and introduced to Australia.