An Etymological Dictionary of Astronomy and Astrophysics

In → predicate logic,
a variable which represents an unspecified → subject. Individual variables work just as do variables in algebra, they stand in for a value, but have no fixed value of their own. They are represented by lower case letters taken from the end of the alphabet x, y, z; and if additional variables are needed by u, v, w, as well.

See also: → individual; → variable.