* Acceleration is a vector quantity: This means acceleration has both magnitude (how fast the velocity is changing) and direction.

* Change in direction means change in velocity: Velocity is also a vector, so changing direction means changing the velocity vector, even if the speed remains constant.

* Change in velocity means acceleration: Since acceleration is the rate of change of velocity, any change in velocity, including a change in direction, results in acceleration.

Examples:

* Car turning a corner: Even if the car maintains a constant speed, it's accelerating because its direction is changing.

* Object moving in a circle: An object moving in a circle at a constant speed is constantly accelerating because its direction is continuously changing.

* Projectile motion: A projectile launched at an angle experiences both horizontal and vertical acceleration, with the horizontal component changing its direction and the vertical component changing its speed.

Key takeaway: Acceleration is not just about speeding up or slowing down; it also encompasses changes in direction.