A door; especially, one of a pair of folding doors, or one
of the leaves of such a door.

One or more membranous partitions, flaps, or folds, which
permit the passage of the contents of a vessel or cavity in one
direction, but stop or retard the flow in the opposite direction; as,
the ileocolic, mitral, and semilunar valves.

One of the pieces into which a capsule naturally separates
when it bursts.

One of the two similar portions of the shell of a diatom.

A small portion of certain anthers, which opens like a
trapdoor to allow the pollen to escape, as in the barberry.

One of the pieces or divisions of bivalve or multivalve
shells.