variable,
n. 1a. an expression that can be assigned any of a set of values.
b. (as modifier) able to take any of a range of values: a variable sum.2. a symbol, such as x, y, or z, representing an unspecified member of a class of objects, numbers, etc. Variables may be used either existentially or universally: in elementary algebra variables occur in conditional equations representing unknown quantities of which the values are to be found. For example, x2 + x = 6, has the solutions x = -3 or 2. However, in an identity such as
(x + y)(x - y) = x2 - y2,
the stated relationship holds for all values of the variables; in the functional notation y = f(x), each value of the argument, the independent variable, x, is associated with a unique value of the dependent variable, y. See also indeterminate, unknown.
b. (as modifier) able to take any of a range of values: a variable sum.2. a symbol, such as x, y, or z, representing an unspecified member of a class of objects, numbers, etc. Variables may be used either existentially or universally: in elementary algebra variables occur in conditional equations representing unknown quantities of which the values are to be found. For example, x2 + x = 6, has the solutions x = -3 or 2. However, in an identity such as
(x + y)(x - y) = x2 - y2,
the stated relationship holds for all values of the variables; in the functional notation y = f(x), each value of the argument, the independent variable, x, is associated with a unique value of the dependent variable, y. See also indeterminate, unknown.