What is a corner kick in football?

Three things must be true: the ball has completely crossed the goal line, the last touch belonged to a defending player, and the ball did not enter the goal. A clearance sliced behind, a goalkeeper's save pushed past the post, or a cross deflected off a defender all produce corners. The kick is taken from the arc nearest to where the ball crossed the line.

The corner flagpost is a fixed part of the setup: it may not be removed, bent or moved to make the kick easier. The ball only needs to touch the lines of the arc to be correctly placed, and the taker may not touch the ball a second time until another player has played it.

The ball must be stationary and is in play once it is kicked and clearly moves. Defenders must stay at least 9.15 metres from the corner arc until the ball is in play, and ignoring that distance can bring a caution. Short corners are fully legal: two attackers combining at the flag to work the ball into a crossing position is a common routine.

There is no offside directly from a corner kick, but the exemption covers only the first delivery. As soon as the ball is in play and a second pass is made, the offside law applies normally. Holding and shoving in the penalty area can be penalised before or during the delivery, and referees increasingly warn players about grappling at corners.

Yes. A ball curled straight into the net from the corner without touching anyone is a valid goal, known in football culture as an olympic goal. It is rare because the angle is extreme and the goalkeeper guards the near post, but in-swinging deliveries with heavy curve occasionally find the net. If the ball somehow travels directly into the taker's own goal, the goal does not stand and the opponents receive a corner.

The real value of corners lies less in direct goals than in the chaos they create. Crosses, headers, flick-ons and second balls all generate chances, which is why a team winning corner after corner has usually pinned its opponent deep inside their own penalty area.