acceleration

The act of accelerating, or the state of being accelerated; increase of motion or action; as opposed to retardation or deceleration.

A falling body moves toward the earth with an acceleration of velocity.

On the East and West Coast Main Lines in the 1950s/60s, for example, we saw the extinction of intermediate stations in order to create the same sort of accelerations that IRP is now promising. Back then, the priority was faster main line services, with wayside/intermediate stations paying the ultimate price.

The amount by which a speed or velocity increases (and so a scalar quantity or a vector quantity).

The boosters produce an acceleration of 20 metres per second per second.

A period of social improvement, or of intellectual advancement, contains within itself a principle of acceleration […]

The change of velocity with respect to time (can include deceleration or changing direction).

The advancement of students at a rate that places them ahead of where they would be in the regular school curriculum.