In anatomy, a viscus (IPA: /ˈvɪskəs/) (plural: viscera /ˈvɪsərə/) is an internal organ of an animal (incluing humans), in particular an internal organ of the thorax or abdomen. The viscera, when removed from a butchered animal, are known collectively as offal. Internal organs are also known as "innards", or less formally, "guts" (which may also refer to the gastrointestinal tract).