Promotion.
Advancement or progress.
The act of furthering or helping forward
The distance by which one wave is behind another.
The extent to which anything is retarded; the result of any retarding or delay; mental, social, or physical slowness.
Deceleration; reduction in the magnitude of velocity.
That which retards; an obstacle; an obstruction.
Extreme stupidity.
A decrease in the speed of telegraph signalling.
A suspension which resolves upwards.
The act of diminishing the rate of speed.