Acceleration

Ac·cel·er·a·tion

The act of accelerating, or the state of being accelerated; increase of motion or action; as, a falling body moves toward the earth with an acceleration of velocity; -- opposed to retardation.
A period of social improvement, or of intellectual advancement, contains within itself a principle of acceleration.
— I. Taylor.

Acceleration of the moon: the increase of the moon's mean motion in its orbit, in consequence of which its period of revolution is now shorter than in ancient times.
Acceleration & retardation of the tides: See Priming of the tides, under Priming.
Diurnal acceleration of the fixed stars: the amount by which their apparent diurnal motion exceeds that of the sun, in consequence of which they daily come to the meridian of any place about three minutes fifty-six seconds of solar time earlier than on the day preceding.
Acceleration of the planets: the increasing velocity of their motion, in proceeding from the apogee to the perigee of their orbits.