Offside is one of the laws in association football, codified in Law 11 of the Laws of the Game. The law states that a player is in an offside position if they are in the opponents' half of the pitch a
An assistant referee signals for offside by raising his flag.
An assistant referee signals that the offside offence was in the middle of the pitch; on the far side the flag would be pointed up at 45 degrees and near the assistant referee it would be pointed down at 45 degrees.
J. C. Thring
Football pitch
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A football pitch or soccer field is the playing surface for the game of association football. Its dimensions and markings are defined by Law 1 of the Laws of the Game, "The Field of Play". The pitch i
Offside (association football)
…football, codified in Law 11 of the Laws of the Game. The law states that a player is in an offside position if they are in the opponents' half of the pitch and closer to the opponents' goal line than both the ball and the second-last opponent (the last opponent is usually, but not necessarily, the goalkeeper…
The goal line at the Stretford End of Old Trafford in Manchester (1992)
A football goal
The penalty area is the large marked rectangular area. The smaller rectangle within it is the goal area (here, the yellow-shirted goalkeeper is the only player in the goal area). The penalty arc is the curved line adjoining the "top" of the penalty area (here, the red-shirted referee is standing near the arc).
Corner arc and flag