What is the term for the change in shape or geometry of a body due to the action of a force?

The term that describes the change in shape or geometry of a body due to the action of a force is "strains." Strain is a measure of deformation representing the displacement between particles in a material body. It is typically expressed as the change in length divided by the original length, indicating how much a material deforms relative to its original dimensions when a force is applied.

Relating this to the context of mechanics, strain occurs in response to applied stresses, which can be caused by various forces acting on the material. While stress refers to the internal resistance to deformation or the force per unit area within materials, strain specifically quantifies how those materials deform. Thus, strain and stress are fundamentally related, but they focus on different aspects—stress on the cause (the force) and strain on the effect (the deformation).

Understanding strain is crucial in machine design as it helps engineers predict how materials will behave under various loading conditions, ensuring the integrity and durability of designed components.