What single word describes motion with zero acceleration?

Motion with zero acceleration is uniform motion, meaning the velocity remains constant in both magnitude and direction.

Acceleration measures how velocity changes with time. If acceleration is zero, an object does not speed up, slow down, or turn. A car traveling in a straight line at a steady speed is a familiar example. An object can also have zero acceleration while remaining completely at rest.

The word “uniform” can cause confusion because everyday language often uses it to mean merely “steady” or “even.” In mechanics, uniform motion is more precise: the object covers equal displacements in equal time intervals and follows a straight path at constant velocity. Constant speed alone is not enough; motion around a circle has constant speed but changing direction, so it has centripetal acceleration.

Newton’s first law connects this idea with force: when the net force is zero, an object maintains its state of rest or uniform motion. This does not mean no forces act; balanced forces can cancel to produce zero net force.