Define structural geology, stress, and strain in rocks.

Structural geology is the study of the three-dimensional distribution of rock units with respect to their deformational histories. Its primary goal is to understand the forces and processes that cause deformation in the Earth's crust.

Stress in rocks is the force applied per unit area on a rock body. It is a measure of the intensity of the forces acting on a rock and can be compressional (squeezing), tensional (pulling apart), or shear (sliding past each other).

Strain in rocks is the deformation or change in shape, size, or orientation that a rock body undergoes in response to applied stress. It can manifest as changes in length, volume, or angle, leading to features like folds, faults, and fractures.