In simplest terms, ductility refers to a materials ability to be stretched into wires. In more technical terms, it is a material property that allows it to deform under tensile stress, without fracture. A related material property is malleability that allows it to be beaten into thin sheets (deformation under compressive stress). Non-ductile materials are also known as brittle materials.
Ductility is a result of metallic bonds between metal atoms. These bonds are formed by delocalized valence electron sharing and allow the atoms to pass over one another, without generating repulsive forces (which lead to fracture).
Some common examples of ductile materials are gold, aluminium and copper. Ductility is of great significance to metal-working. Brittle materials can not be used for metalworking.
The ductility of a material can be altered by changing conditions. For examples, materials are less ductile at lower temperature. Similarly, increase in temperature will cause higher ductility.
Hope this helps.
The bendability or malleability of an item. Usually a metal. Aluminum foil for example is very ductile because it can be crushed and then straightened out again, over and over.