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Metals when heated, expand in volume. The coefficient of thermal expansion is the liner measure of this expansion. It give a unit change in the liner dimension per unit increase in temperature. Note that the term used in the description above is change, because coefficient of thermal expansion also gives the change in dimension as contraction as the metal cools. But the expansion and contraction with the change in the temperature is not just liner, it is volumetric. Engineering data and table only give the Liner values as coefficient of thermal expansion.

The volumetric expansion is of interest to welding engineers, and fabricators, because the expansion and subsequent cooling causes shrinkages and distortions in the structure. A welding engineer is concerned about these changes in dimension and provides solutions to avoid, or eliminate the effect of thermals effect on the dimension of the weldment.