motion

Motion most commonly means movement.

To set in motion means to cause something to start moving. It’s usually used in a figurative way meaning to start, initiate, or cause something to begin (the phrase often implies that it’s something that might not be able to be stopped once it’s started).

A person’s (or animal’s) motion while walking is called their gait.

Sometimes, a motion is a gesture. Both words can also be used as verbs, as in He motioned/gestured toward the door. The word nod is used in reference to a motion or gesture made with the head. Nod can also be used as a verb or a noun.

In the context of a formal meeting, a motion is a formally made proposal or suggestion. Such motions often must be “seconded” (agreed with by one other person) to be considered. In this context, motion can also be used as a verb. The verb propose is a synonym.

The words motion and movement are very similar. Both can be used generally to indicate that the things being observed are moving, though movement is perhaps more general. For example, you might point out the movement of the trees during a windstorm, or comment on the lively movement of people at a train station.

Both can also be applied in the context of a single thing that’s moving. Motion is perhaps more common when discussing the mechanics of how something moves. For example, astronomers study the motion of the planets.

Motion may be more commonly used in descriptions of specific types of moving, as in a swinging motion or a running motion.

Motion is used in the phrase in motion, which is used to describe something that’s moving.

Of course, motion and movement both have many other more specific meanings, such as a formal motion during a meeting, a movement in a piece of music, or a social movement.