What term describes the internal resistance or force of a body?

The term that describes the internal resistance or force of a body is strain. In the context of materials and engineering, strain refers to the deformation or displacement of a material in response to an applied force or load. When a material is subjected to stress (an external force applied per unit area), it consequently undergoes strain, which quantifies how much the material's shape or length changes as a result.

Strain is typically expressed as a ratio, measuring the amount of deformation relative to the original dimensions of the material. This concept is crucial in engineering, as it helps in understanding how materials will behave under different loads and conditions, allowing engineers to design structures and components that can sustain these internal forces without failing.

In contrast, the other terms relate to different aspects of material behavior: stress refers to the external force applied, load refers to the weight or force exerted on an object, and pressure typically measures the force exerted perpendicular to the surface of an object. Understanding the distinction between these terms is essential for accurate analysis in engineering applications.