Final answer:
The stiffness of a dental gold alloy is expressed as its modulus of elasticity, also known as Young's modulus, which indicates how stiff the material is.
Step-by-step explanation:
The measure of the stiffness of a dental gold alloy would be expressed as its modulus of elasticity. This is often referred to as Young's modulus, which is a measure of a material's ability to withstand changes in length when under lengthwise tension or compression. It can be thought of as a measure of how stiff a material is. Young's modulus is defined as the ratio of stress (force per unit area) to strain (proportional deformation) and is expressed in Pascal (Pa). In essence, materials with a higher Young's modulus will deform less under a given load, indicating a greater stiffness.