Final answer:
Strain, represented by the Greek letter epsilon (ε), is shown on the horizontal axis of a stress-strain diagram, which graphically displays the deformation of materials under stress.
Step-by-step explanation:
In the field of material science and engineering, strain is a dimensionless number that represents the deformation of a material under stress. Strain is typically represented by the Greek letter epsilon (ε) and graphically shown on the horizontal axis of a stress-strain diagram. The vertical axis of this diagram represents stress, often denoted by the Greek letter sigma (σ). A stress-strain diagram details the behavior of a material when subjected to forces, showing how it deforms (strain) in response to applied stress. The relationship between stress and strain for most materials initially follows Hooke's Law, where the stress is directly proportional to the strain.