Aperture

n.	1.	The act of opening.
	2.	An opening; an open space; a gap, cleft, or chasm; a passage perforated; a hole; as, an aperture in a wall. An aperture between the mountains. - Gilpin. The back aperture of the nostrils. - Owen.
	3.	(Opt.) The diameter of the exposed part of the object glass of a telescope or other optical instrument; as, a telescope of four-inch aperture.

Noun	1.	aperture - a device that controls amount of light admitted
	2.	aperture - a natural opening in something
	3.	aperture - an man-made opening; usually small

access, aisle, alley, ambulatory, arcade, artery, avenue, bore, breach, break, broaching, channel, check, chink, clearing, cleft, cloister, colonnade, communication, conduit, corridor, covered way, crack, crevice, cut, defile, disclosure, discontinuity, exit, fenestra, ferry, fissure, fistula, fontanel, foramen, ford, gallery, gape, gash, gat, gulf, hiatus, hollow, inlet, interchange, intersection, interstice, interval, junction, lacuna, lane, laying open, leak, opening up, orifice, outlet, overpass, pass, passage, passageway, perforation, pinhole, portico, prick, puncture, railroad tunnel, rupture, slash, slit, slot, space, split, stoma, throwing open, traject, trajet, tunnel, uncorking, underpass, unstopping, vent, yawn