A folding door. Swift through the valves the visionary fair repass’d.

A lid or cover so formed as to open a communication in one direction, and close it in the other. Thus the valve of a common pump opens upwards to admit the water, and closes downwards to prevent its return.

In anatomy, a membranous partition within the cavity of a vessel, which opens to allow the passage of a fluid in one direction, and shuts to prevent its regurgitation.

In botany, the outer coat, shell or covering of a capsule or other pericarp, or rather one of the pieces which compose it; also, one of the leaflets composing the calyx and corol in grasses.

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