nonmotion

Nonmotion is the state or condition of having no motion. In physics and everyday language, it refers to the absence of movement in which an object's position does not change with respect to a chosen frame of reference. The term is often used to denote rest, though its precise meaning depends on the reference frame and whether instantaneous velocity or sustained immobility is being described.

In classical mechanics, an object is in nonmotion relative to a reference frame if its velocity is zero at the given moment and remains zero over a period of time. Motion is relative, so an object that is nonmotion in one frame may be moving in another; different observers can assign different states of motion based on their own frames of reference.

In the theory of relativity, there is no absolute nonmotion. All motion is relative to an observer, and there is no privileged frame of reference in which all objects are at rest. An object that is nonmotion in one inertial frame may be moving in another, and vice versa, depending on how the frame is defined and how velocity is measured.

Measurement and terminology commonly associated with nonmotion include zero speed, zero displacement over a time interval, and a zero velocity vector relative to a chosen reference frame. In practice, nonmotion is a convenience for describing stationary states in physics, engineering, and everyday life, while acknowledging the relativity of motion.

Beyond physics, nonmotion can appear in discussions of still imagery, static states in art, or philosophical inquiries into change and permanence.