In many team sports, defense or defence (see spelling differences) is the action of preventing an opponent from scoring. The term may also refer to the tactics involved in defense, or a sub-team whose primary responsibility is defense. Similarly, a defense player is a player who is generally charged with preventing the other team's forwards from being able to bear down directly on their own team's goalkeeper. Such intention exist in association football, ice hockey, water polo and many other sports.

In ice hockey, there are normally two defensemen on the ice. One is usually a more offensive player better known for their ability to glean assists or goals rather than for their strong defensive play. Such players are known as offensive defenseman. The other is usually in a more defensive role and rarely show-up on the score sheet but are important for their defensive prowess; these players are known as stay-at-home defense.

In water polo, if an offensive player, such as the center forward, has the ball in front of the goal, and the defender cannot steal the ball, he may intentionally commit a foul. The forward then has a free throw but must pass the ball off to another offensive player, rather than making a shot at the goal. Defensive perimeter players may also intentionally cause a foul and then move toward the goal, away from their attacker, who must take a free throw. This technique, called 'sloughing', allows the defense an opportunity to double-team the center forward and possibly steal the inbound pass. The water polo referee may refrain from declaring a foul caused by a defensive player, if in his judgment this would give the advantage to the defending team. This is known as the Advantage Rule.

Defence (see -ce/-se) may refer to:

Sport (or, in the United States, sports) is all forms of competitive physical activity which, through casual or organised participation, aim to use, maintain or improve physical fitness and provide entertainment to participants. Hundreds of sports exist, from those requiring only two participants, through to those with hundreds of simultaneous participants, either in teams or competing as individuals.

Sport is generally recognised as activities which are based in physical athleticism or physical dexterity, with the largest major competitions such as the Olympic Games admitting only sports meeting this definition, and other organisations such as the Council of Europe using definitions precluding activities without a physical element from classification as sports. However, a number of competitive, but non-physical, activities claim recognition as mind sports. The International Olympic Committee (through ARISF) recognises both chess and bridge as bona fide sports, and SportAccord, the international sports federation association, recognises five non-physical sports, although limits the amount of mind games which can be admitted as sports.