1. (in animal anatomy) Any enclosing cluster of cells that protects and nourishes a cell or structure within. For example, follicles in the ovary contain developing egg cells, while hair follicles envelop the roots of hairs.

2. (in botany) A dry fruit that, when ripe, splits along one side to release its seeds. It is formed from a single carpel containing one or more seeds. Follicles do not occur singly but are grouped to form clusters (etaerios). Examples include larkspur, columbine, and monk’s hood.