Velocity
Etymology
From Latin "velocitas", from "velox" (swift). English kept it as a near-synonym for speed until physics gave it the stricter meaning that includes direction.
noun · /veh-LOSS-ih-tee/
Speed together with the direction of travel.
What it names
The fact that direction matters as much as pace, which is why a car rounding a curve at a constant speed is still changing its velocity.
Example
Two planes fly at 500 mph, but with opposite velocities they close the gap at 1,000 mph.
Related idea
Speed is just how fast; velocity is how fast and which way. This is why acceleration can happen at steady speed — a turn changes direction, and so changes velocity.