chance

It's the chance of a lifetime.

a chance to escape.

a chance encounter; a chance result.

(at) snatch at the chance of

Chance will determine the outcome.

They met by chance on a plane.

an even chance of winning.

a chance to strike a blow for freedom.

there is a chance of winning the raffle.

there was just a slim chance of success.

It's a good chance to broach the subject.

watch a chance (an opportunity)

a fifty-fifty chance to live

They have not an earthly chance to win.

was panting for a chance to play.

a better chance of success.

snap at a chance to go to China.