opportunity

opportunity knocks a chance of success occurs.

☞ This expression comes from the proverb opportunity never knocks twice at any man's door or opportunity knocks but once. The form of the saying with opportunity dates from the late 19th century, but fortune was used in the early 19th century and a version of the saying is recorded in medieval French. It reached a wider audience as the title of an ITV talent show (1956–78) hosted by Hughie Green.