The Coefficient of Linear Expansion is a measure of how much a material expands or contracts when its temperature changes. It is defined as the change in length per unit length of the material for each degree of temperature change. Different materials have different coefficients, which means they expand or contract at different rates when heated or cooled. This property is important in various applications, such as in the design of structures and machinery. For example, when constructing bridges or railways, engineers must consider the coefficient of linear expansion of materials like steel and concrete to ensure safety and stability under temperature fluctuations.