In the context of material properties, what is meant by ‘toughness’?

Toughness is a critical material property that defines a material's ability to absorb energy and undergo plastic deformation without fracturing. This characteristic is particularly important in applications where materials are subjected to impact or stress, as it indicates how well a material can withstand sudden forces or stresses without breaking.

In essence, toughness involves a combination of strength and ductility. A tough material can endure significant amounts of stress and still deform rather than break, which is vital in structures that need to withstand dynamic or fluctuating loads. This ability to absorb energy before failure is what distinguishes toughness from other material properties.

The other options address different material properties: the first option focuses on resistance to permanent deformation, which relates more to hardness or yield strength. The third option speaks to electrical conductivity, which is not related to toughness. Lastly, the fourth option refers to ductility, specifically the capability to be stretched, but does not encompass the energy absorption aspect that is integral to defining toughness. Thus, the correct understanding of toughness directly aligns with the provided definition in the correct choice.