Umpire (baseball)

In baseball, the umpire is the person charged with officiating the game, including beginning and ending the game, enforcing the rules of the game and the grounds, making judgment calls on plays, and handling the disciplinary actions. The term is often shortened to the colloquial form ump. They are also sometimes addressed as blue at lower levels due to the common color of the uniform worn by umpires. In professional baseball, the term "blue" is seldom used by players or managers, who instead call the umpire by name. Although games were often officiated by a sole umpire in the formative years of the sport, since the turn of the 20th century, officiating has been commonly divided among several umpires, who form the umpiring crew.

In a game officiated by two or more umpires, the umpire in chief (or home plate umpire) is the umpire who is in charge of the entire game. This umpire calls balls and strikes, calls fair balls, foul balls short of first/third base, and makes most calls concerning the batter or concerning baserunners near home plate. To avoid injury, the home plate umpire wears the same mask the catcher wears. If another umpire leaves the infield to cover a potential play in foul ground or in the outfield, then the plate umpire may move to cover a potential play near second or third base. (The umpire-in-chief should not be confused with the crew chief, who is often a different umpire; see below.) In the event that an umpire is injured and only three remain, the second base position will generally be left vacant.

In nearly all levels of organized baseball, including the majors, an umpiring crew rotates so that each umpire in the crew works each position, including plate umpire, an equal number of games. In the earliest days of baseball, however, many senior umpires always worked the plate, with Hall of Fame umpire Bill Klem being the last umpire to do so. Klem did so for the first 16 years of his career. On the Major League level, an umpiring crew generally rotates positions clockwise each game. For example, the plate umpire in one game would umpire third base in the next.

Other umpires are called base umpires and are commonly stationed near the bases. (Field umpire is a less-common term.) When two umpires are used, the second umpire is simply the base umpire. This umpire will make most calls concerning runners on the bases and nearby plays, as well as in the middle of the outfield. When three umpires are used, the second umpire is called the first-base umpire and the third umpire is called the third-base umpire, even though they may move to different positions on the field as the play demands. These two umpires also call checked swings, if asked by the plate umpire (often requested by catcher or defensive manager; however, only the plate umpire can authorize an appeal to the base umpire): the first base umpire for right-handed batters, and the third base umpire for left-handed batters; to indicate a checked swing, the umpire will make a "safe" gesture with his arms. To indicate a full swing, he will clench his fist.

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Wikipedia