On trouve le terme non traduit assez régulièrement, comme souvent en informatique. Sinon, il me semble que "variable libre" pourrait constituer un équivalent correct.


In mathematics, and in other disciplines involving formal languages, including mathematical logic and computer science, a free variable is a notation for a place or places in an expression, into which some definite substitution may take place, or with respect to which some operation (summation or quantification, to give two examples) may take place. ...