Final answer:
Stress is represented by the symbol σ and is plotted on the vertical y-axis of a stress-strain curve, while strain is represented by the symbol ε and is plotted on the horizontal x-axis.
Step-by-step explanation:
In the context of a stress-strain curve, stress is typically represented by the symbol σ (sigma) and is plotted on the vertical y-axis. Stress, defined as the ratio of force to area (F/A), is measured in units of pressure, such as Pascal (N/m²). Strain, on the other hand, is represented by the symbol ε (epsilon) and is plotted on the horizontal x-axis. It is unitless as it is the ratio of the change in length to the original length of a material under stress. The stress-strain curve is used to display the relationship between stress and strain for a given material, and it characterizes how a material deforms under varying levels of stress. Point H on the curve indicates the limit of proportionality, while point E is the elastic limit, beyond which the material will not return to its original shape.