Definition:Bound Variable

Definition
A bound variable is a variable which, when it occurs in an expression, can be replaced with another variable without changing the meaning of the statement.

Examples
In algebra:
 * $x^2 + 2 x y + y^2 = \paren {x + y}^2$

both $x$ and $y$ are bound variables.

Also known as
A bound variable is also popularly seen with the name dummy variable. Both terms can be seen on.

In treatments of pure logic, this is sometimes known as an individual variable.

Some sources call it an apparent variable, reflecting the fact that it only "appears" to be a variable.

Also see

 * Definition:Bound Occurrence