Main Entry: cap·sule

Pronunciation: \ˈkap-səl, -(ˌ)sül\

Function: noun

1 a : a membrane or saclike structure enclosing a part or organ <the capsule of the kidney>

[capsule illustration]

b : either of two layers or laminae of white matter in the cerebrum: (1) : a layer that consists largely of fibers passing to and from the cerebral cortex and that lies internal to the lentiform nucleus—called also internal capsule (2) : one that lies between the lentiform nucleus and the claustrum—called also external capsule
2 : a shell usually of gelatin for packaging something (as a drug or vitamins) ; also : a usually medicinal or nutritional preparation for oral use consisting of the shell and its contents
3 : a viscous or gelatinous often polysaccharide envelope surrounding certain microscopic organisms (as the pneumococcus)