ഒരു വസ്തുവിന് ഭംഗം സംഭവിക്കാതെ പ്ലാസ്തിക വിരൂപണത്തിന് വിധേയമാകാനുളള കഴിവിനെയാണ് കടുപ്പം (Toughness) എന്നുപറയുന്നത്.

In materials science and metallurgy, toughness is the ability of a material to absorb energy and plastically deform without fracturing. Toughness is the strength with which the material opposes rupture. One definition of material toughness is the amount of energy per unit volume that a material can absorb before rupturing. This measure of toughness is different from that used for fracture toughness, which describes the capacity of materials to resist fracture. Toughness requires a balance of strength and ductility.