When is a penalty stroke awarded?

FIH Rule 12.4: a penalty stroke is awarded:

• for an offence by a defender in the circle that prevents the probable scoring of a goal, or
• for an intentional offence in the circle by a defender against an opponent who has possession of the ball or an opportunity to play it.

Compare this with a penalty corner, which is given for an offence in the circle that does not prevent a probable goal, or an intentional offence against an opponent without possession or an opportunity to play the ball.

If there's another offence or misconduct before an awarded penalty is taken, you may award a more severe penalty, give a personal penalty, or reverse the penalty if the team first awarded it committed the later offence (Rule 12.5).