Each play constitutes a down. The offence must advance the ball at least ten yards towards the opponents' goal line within three downs or forfeit the ball to their opponents. Once ten yards have been gained the offence gains a new set of three downs (rather than the four downs given in American football). Downs do not accumulate. If the offensive team completes 10 yards on their first play, they lose the other two downs and are granted another set of three. If a team fails to gain ten yards in two downs they usually punt the ball on third down or try to kick a field goal (see below), depending on their position on the field. The team may, however use its third down in an attempt to advance the ball and gain a cumulative 10 yards.
If it is possible to answer this question, answer it for me (else, reply "unanswerable"): What is another term for a completed play?
down