In sports, a loan involves a particular player being to temporarily play for a club other than the one he is currently contracted to. Loan deals may last from a few weeks to all season-long and can also subsist for multiple seasons.
Players may be loaned out to other clubs for several reasons. Most commonly, young prospects will be loaned to a club in a lower league in order to gain valuable first team experience. In this instance, the parent club may continue to pay the player's wages in full or in part. Some clubs put a formal arrangement in place with a feeder club for this purpose, such as Manchester United and Royal Antwerp, Arsenal and Beveren, or Chelsea and Vitesse. In other leagues such as Italy's Serie A, some smaller clubs have a reputation as a "farm club" and regularly take players, especially younger players, on loan from larger clubs.
A club may take a player on loan if they are short on transfer funds but can still pay wages, or as temporary cover for injuries or suspensions. The parent club might demand a fee and/or that the loaning club pays some or all of the player's wages during the loan period. A club might seek to loan out a squad player to make a saving on his wages, or a first team player to regain match fitness following an injury.
A loan may be made to get around a transfer window. Such a loan might include an agreed fee for a permanent transfer when the next transfer window opens.
Some players are loaned because they are unhappy or in dispute with their current club and no other club wishes to buy them permanently. Examples of this situation include Henri Camara with Wolverhampton Wanderers, Craig Bellamy with Newcastle United, and Darren Bent with Aston Villa.
In the Premier League, players on loan are not permitted to play against the team which holds their registration (section 7.2 of rule M.6). Loanees are, however, allowed to play against their 'owning' clubs in cup competitions, unless they have played for their owning club in that cup during that season.
In the Scottish Professional Football League (and previously the Scottish Football League), clubs are permitted to take players on as unpaid trialists even for competitive fixtures. Sometimes for the first two weeks of a trial period players' names are obfuscated; match reports use the convention "A Trialist" to refer to such players in lieu of using their real names.