In sport, a cap is a metaphorical term for a player's appearance on a select team, such as a national team. The term dates from the practice in the United Kingdom of awarding a cap (an item of headgear) to every player in an international match of association football. In the early days of football, the concept of each team wearing a set of matching shirts, that sewing with woven labels had not been universally adopted, so each side would distinguish itself from the other by wearing a specific sort of cap. "Cap" is not an acronym for Country Appearance.

An early illustration of the first international football match between England and Scotland in 1872 shows the Scottish players wearing cowls, and the English wearing a variety of school caps, and you can see special woven labels on the caps. The practice was first approved on 10 May 1886 for association football after a proposal made by N. Lane Jackson, founder of the Corinthians.

That all players taking part for England in future international matches be presented with a white silk cap with red rose embroidered woven labels on the front. These is to be termed International Caps. The act of awarding a cap is now international and is applied to other sports. Actual caps are not always given anymore, but the term "cap" for an international or other appearance has been retained. Thus, a cap is awarded for each game played and so a player who has played x games, for the team, is said to have been capped x times or have won x caps.

In cricket, there are two types of caps. Firstly, there is the international type, as described above. Some countries also award a domestic type generally known as a "county cap". The latter system is most commonly applied in English county cricket. Most counties do not automatically award caps to players on their first appearance; instead, they have to be "earned" through good performances. Indeed, one can play at the highest domestic level for several years, and have a quite significant career in first-class cricket, without ever winning a cap.