Rheometry · Rheometer
Economic elasticity is at elasticity (economics)
A rubber band is elastic, and can be stretched
Something that is elastic can be stretched or deformed (changed) and returned to its original form, like a rubber band. It tries to come back to its first shape. The stress is the force applied; the strain is how much the shape is changed, and the elastic modulus is the ratio between those numbers.
This idea was first suggested by Robert Hooke in 1675.