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One who holds an office or place, especially as a deputy, proxy, or appointed government official.

In a mathematical or logical expression, a symbol that may be replaced by the name of any element of a set.

In the decimal form of a number, a digit that is not significant.

Something used or included temporarily or as a substitute for something that is not known or must remain generic; that which holds, denotes or reserves a place for something to come later.

a person authorized to act for another

a symbol in a logical or mathematical expression that can be replaced by the name of any member of specified set