coel(o)- Also coelio-. In the US, cel(o)- or celio-.
[Greek koilia, belly; koilos, hollow; koilōma, cavity.]
The usual medical sense is of the abdomen: coelioscopy is a technique of viewing abdominal organs through an incision in the abdominal wall; the usual adjective relating to the abdomen is coeliac. The coelom (US sometimes celom) is the principal body cavity in most animals, located between the intestinal canal and the body wall. Animal example include the coelacanth (Greek akantha, spine, so ‘having hollow spines’), an ancient species of fish, and coelenterate (Greek enteron, intestine), a member of a group that includes jellyfish and sea-anemones. However, the astronomical instrument called a coelostat, comes—irregularly—from a different root, Latin caelum, sky.