Originally Posted by
beardy
Velocity is a vector in and of itself.
It's a usage thing. velocity is certainly a vector quantity, but when people use the term "velocity" they commonly mean "speed" anyway.
Velocity (being as you say a vector) has two elements - a magnitude and a direction. When people use the expression "velocity vector" the parameter they're usually talking about is just the "direction" element and the magnitude is not of interest. Whoever the first person was who coined the phrase to name a symbol on a display decided that "Velocity Vector" was a good name for the parameter "the direction the speed is travelling in". Aviation, like so many other fields, has terms evolved through usage which no longer make literal sense.
Life's like that. In fact ironically the term "tautology" itself is another example, but that's for another thread.
PDR