Non-competitive inhibition is a type of enzyme inhibition where the inhibitor reduces the activity of the enzyme and binds equally well to the enzyme whether or not it has already bound the substrate.
If the inhibitor may bind to the enzyme whether or not the substrate has already been bound, but has a higher affinity for binding the enzyme in one state or the other, it is called a mixed inhibitor.
Read more about Non-competitive Inhibition: Terminology, Mechanism, Equation, Example: Noncompetitive Inhibitors of CYP2C9 Enzyme