# equivalence principle

The equivalence principle is the complete equality of gravitational and inertial mass, gravity, and acceleration, and the identification of free-falling frames with inertial frames. The equivalence principle is the fundamental basis for the general theory of relativity.

The **weak (or Newtonian) equivalence principle** is the principle
that the laws of mechanics are the same in inertial
frames of reference. This implies that gravitational mass and inertial
mass are equivalent. **The strong (or Einstein) equivalence principle** is the principle that *all* physical laws, not just those of mechanics,
are the same in all inertial and freely falling frames of reference.