Newton's first law of motion is sometimes described as the law of inertia.

Here's why:

* Inertia is the tendency of an object to resist changes in its motion. This means an object at rest will stay at rest, and an object in motion will stay in motion at a constant velocity, unless acted upon by a net force.

* Newton's first law states exactly this: "An object at rest stays at rest, and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force."

Therefore, the law of inertia perfectly summarizes the key concept of Newton's first law.