Definition:Binding Constraint

Definition
Let $\RR$ be a weak inequality on some set $S$.

Let $a \mathrel \RR b$ be a constraint given by a weak inequality $\RR$.

Let $P \in S$ such that $P \mathrel \RR b$ is an equality.

Then $a \mathrel \RR b$ is binding at $P$.

Also known as
A binding constraint is also known as an active constraint.