A hockey pitch is the playing surface for the game of field hockey. Historically, the game was played on natural turf (grass) but nowadays it is predominantly played on an artificial turf. The transition onto artificial pitches came during the 1970s and was made mandatory for major competitions in 1976. All the lines, markings and goal specifications are outlined by the International Hockey Federation in "The Rules of Hockey".
All line markings on the pitch form part of the area which they define. For example, a ball on the side line is still in the field of play; a ball on the line of the penalty circle is in the penalty circle; a foul committed over the 23-metre (25-yard) line has occurred in the 23-metre area. A ball must completely cross a boundary line to be out of play, and a ball must wholly cross the goal line before a goal is scored.
Due to the original formulation of the rules in England, the standard dimensions of a hockey pitch were originally expressed in imperial units. The rules are now expressed explicitly in metric dimensions (since 1998), although the use of the imperial terms remains common in some countries.