Same word as opportunity:

befalling, break, connection, contingency, convenience, cut, event, excuse, fair shake, fighting chance, fitness, fling, fortuity, freedom, go, good fortune, good luck, happening, hope, hour, iron in the fire, juncture, leisure, liberty, moment, occasion, one's move, one's say, one's turn, opening, pass, prayer, probability, relief, room, run, scope, shot, show, space, spell, squeak, stab, the hunt, the running, time, turn, whack