Ductility is strictly defined as the ability of a material to be drawn into a wire. More generally, it is used to refer to the amount of plastic deformation a material can endure before failure.

Ductility is not a uniquely defined material property, quantifiable by a single test. Instead, there are a number of tests that are used to give a measure of ductility.

The test chosen will usually depend on the application in which the alloy is to be used.