* Friction is the force: Friction is the force that opposes motion between two surfaces in contact. In the case of terminal velocity, it's the air resistance (a type of friction) acting on a falling object.
* Terminal velocity is the result: As an object falls, its speed increases. This increases the air resistance acting against it. Eventually, the air resistance force equals the force of gravity pulling the object down. At this point, the net force on the object is zero, and it stops accelerating. This constant speed is called terminal velocity.
Think of it this way:
* Friction is the brakes: Air resistance acts like brakes on a falling object.
* Terminal velocity is the speed limit: The brakes get stronger as the object falls faster, eventually limiting the speed to a constant value.
Therefore, terminal velocity is a consequence of friction, specifically air resistance.
