Let us compare the motions of two bodies. Let the motion of one body be the *reference* motion. Let the motion of the other body be the *comparative* motion. Let the two bodies begin together at one place.

Definitions:

A *place* is the general term for an answer to *Where?* A *point-place*, or simply a *point*, is the smallest place. A *translation* is a vector from one point-place to another. Travel distance is the arc length of the trajectory of a motion, which includes any retracing of the trajectory.

Space and time refer to different perspectives of the universe of motion.

*Space* is the locus of all potential places for the *comparative* motion, which is said to be “in space.” *Displacement* is a translation vector from one point to another point of the *comparative* motion. The travel distance from the beginning point to the ending point of the *comparative* motion, is the *travel length* for a motion in space.

*Time* is the locus of all potential places for the *reference* motion, which is said to be “in time.” *Dischronment* is a translation vector from one point to another point of the *reference* motion. The travel distance from the beginning point to the ending point of the *reference* motion, is the *travel time* for a motion in time.