Constant speed
An object is not accelerating when it is moving in a straight line at an unchanging speed (which may be zero).
zero
His motion will be uniform if he is running in constant speed.
Our theories of physics indicate that the speed of light should be invariant (unchanging) anywhere in the universe.
Constant speed
An unchanging speed is constant.
Average speed is a representation of all your speeds between two points, constant speed is just unchanging speed.
An object is not accelerating when it is moving in a straight line at an unchanging speed (which may be zero).
zero
Velocity magnitude is unchanging at constant speed. The direction might change (velocity is a vector with both size (speed) and direction) if , for example, you are driving around a curve at a constant speed.
His motion will be uniform if he is running in constant speed.
Acceleration in motion refers to a change in speed or direction of that object's motion. So a type of motion in which speed and direction do not change is a motion in which the acceleration is constant (i.e. unchanging).
The duration of The Unchanging Sea is 840.0 seconds.
Our theories of physics indicate that the speed of light should be invariant (unchanging) anywhere in the universe.
The Unchanging Sea was created on 1910-05-05.
Your Unchanging Love was created on 1967-06-13.