spring constant k

The spring constant, a.k.a. the force constant of the spring or just the force constant if it is clear that a spring is under discussion, is a measure of the stiffness of a spring. It is the force-per-amount-of-stretch-or-compression of the spring.

S.I. Units: N/m, newtons per meter

Pitfall Avoidance Notes: The symbol for the spring constant is a lower case k. Don't use an upper case K and don't confuse the spring constant k with the kinetic energy of an object. The symbol for kinetic energy is upper case K.