Redshirt/Greyshirt
While both recipients of grey and red shirts attend classes at a school before participating in football games, the difference is in the player-to-be's time of enrollment:
Via John Mackovic of The Desert Sun: "Grey shirt is a term used to designate an incoming freshman who waits until the second semester to enroll rather than the fall. College athletes are allowed a five year calendar to play four seasons. The calendar begins once one is enrolled. By waiting until the spring to start college, a player will be playing his last season in the sixth year after high school rather than the fifth. "
In contrast, infoplease.com explains that "When a player is given the "red-shirt" designation by his or her coach, that means he or she has participated in a college's academic year, but did not participate during that year's sports season. Most likely a "red-shirt freshman" in college football is a sophomore in college who practiced with the team his first year, but did not play in any games (at the coach's request), or was seriously injured during his first season." By redshirting, a player gains an opportunity to learn schemes and techniques, rehabilitate an injury, learn a new position and/or physically develop without losing a year of eligibility.
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