 Ductility is a measure of the material's ability to undergo significant plastic deformation before rupture, which may be expressed as percent elongation or percent area reduction from a tensile test. According to Sheet-Lease Mechanical Engineering Design Temp Education 1 significant de-notes about 5.0 percent elongation section 5.3, page 233. See also EEC 2212, page 54 definitions of percent elongation and percent area reduction. Ductility is often characterized by a material's ability to be stretched into a wire. From examination of data in tables A20, A21, A22, A23, and A24 in Sheet-Lease Mechanical Engineering Design, Temp Education 1 for both ductile and brittle materials, it is possible to postulate a broader quantifiable definition of ductility that does not rely on percent elongation alone. In general, a ductile material must have a measurable yield strength, at which unrecoverable plastic deformation begins. See yield engineering and also must satisfy one of the following conditions, either have an elongation to failure of at least 5 percent, or area reduction to rupture at least 20 percent, or true strain, to rupture at least 10 percent. Merrily Ability, a similar property, is a material's ability to deform under compressive stress. This is often characterized by the material's ability to form a thin sheet by hammering or rolling. Both of these mechanical properties are aspects of plasticity, the extent to which a solid material can be plastically deformed without fracture. Also, these material properties are dependent on temperature and pressure investigated by Percy Williams Bridgman as part of his note-belt prize-winning work on high pressures. Ductility and mediability are not always co-extensive, for instance, while gold has high ductility and mediability, lead has low ductility but high merrily ability.The word ductility is sometimes used to encompass both types of plasticity.3.