Definitions

1. noun

A point in the orbit of a celestial body, especially the farthest or nearest point from the body it revolves around.

“The planet’s apsis is where it reaches its maximum or minimum distance from the sun.”

2. noun

The point or curve in a periodic or oscillating motion or system, especially when it is farthest from or nearest to its equilibrium position.

“The pendulum’s apsis marked the point of its maximum swing.”