Noun
(programming) A variable that is not bound to a storage location.
(mathematics, logic) A variable (occurring within some expression or well-formed formula) which is not bound by a quantifier or analogous symbol (such as a lambda abstractor, the "differential d" near the end of an integral or differential form, or a summation symbol).
Source: en.wiktionary.orgA typing context assigns a type to each free variable. Source: Internet
However, and (where is a free variable) are not because both are in normal form and they are not the same. Source: Internet
The choice of the free variable used in the form F(x) is not relevant to the assignment of the Gödel number G(F). Source: Internet