Capsule has many meanings in medicine including the following:
In medicine, a membranous structure that envelops an organ, a joint, tumor, or any other part of the body. It is usually made up of dense collagen-containing connective tissue.
In pharmacy, a solid dosage form in which the drug is enclosed in a hard or soft soluble container, usually of a form of gelatin.
In microbiology, a coat around a microbe, such as a bacterium or fungus.