The term is used as a verb, noun, and adjective. For example, a coach may choose to redshirt a player who is then referred to as a redshirt freshman or simply a redshirt.
The term has also been adopted to elementary education where it refers to the practice of delaying a child's entrance into kindergarten by a year to give the child an opportunity for further mental, physical, or socioemotional growth.
The term is also used in American professional football. In this instance, a red jersey is worn by a player - usually the team's starting quarterback - during practice and signifies that the player is not to be tackled or hit during practice to prevent injury to a critical member of the team.
An athlete may be asked to redshirt if he or she would have no opportunity to play as an academic freshman. This is a common occurrence in many sports where there is already an established starter or too much depth at the position in which the freshman in question is planning to play.
There is also a medical redshirt that may be obtained to replace a season lost to injury. A medical redshirt can be granted by the governing body for a season lost completely or almost completely to injury. A medical redshirt can allow a player to gain additional eligibility beyond the standard four academic calendar years. On rare occasions, a player may be allowed to play in his or her sixth year of college if he or she suffered a serious injury which kept him or her from playing for more than one season.
The term redshirt freshman indicates an academic sophomore (second-year student) who is in the first season of athletic eligibility. A redshirt freshman is distinguished from a true freshman (first-year student) as one who has practiced with the team for the prior season. The term redshirt sophomore is also commonly used to indicate an academic junior (third-year student) who is in the second season of athletic eligibility. After the sophomore year the term redshirt is rarely used, instead the terms fourth year junior and fifth year senior are more common.
Athletes may also utilize a grayshirt year in which they attend school, but cannot enroll as a full-time student, and do not receive a scholarship for that year. This means that they are an unofficial member of the team and do not participate in practices, games, or receive financial assistance from their athletic department. Typically, grayshirts occur when a player is injured right before college and requires an entire year to recuperate. Rather than waste his or her redshirt, the player can attend school as a part-time regular student and then join the team later.
While the redshirt status may be conferred by a coach at the beginning of the year, it is not confirmed until the end of the season, and more specifically, it does not rule a player ineligible in advance to participate in the season. If a player shows great talent, or there are injuries on the team, the coach may remove the redshirt status and allow the player to participate in competition for the remainder of the year.
However, NCAA rules are quite clear on the use of redshirt status: any participation in any competition counts as a season of eligibility. For example, even a single play in a football game counts as participation, so coaches cannot play redshirt players at the end of a game simply to get them some experience. This contrasts with high school classifications of varsity and junior varsity, where JV players are sometimes allowed to play at the varsity level without using an additional year of eligibility.
The first athlete known to extend their eligibility in the modern era of redshirting was Warren Alfson of the University of Nebraska in 1937. Alfson requested that he be allowed to sit out his sophomore season, due to the number of experienced players ahead of him; also, he had not attended college until several years after graduating high school, and felt he needed more preparation. The year of preparation worked; Alfson was All-Big Six Conference in 1939 and an All-American guard in 1940.