CEASELESS LEARNING: velocity and acceleration

We now that acceleration is the rate of change of velocity.

Constant acceleration 1m/s² means that the change of velocity is +1m/s per sec.
Constant acceleration -1m/s² means that the change of velocity is -1m/s per sec.

We also know that positive velocity in one-dimensional motions means motion to the positive direction which is usually to the right.
Since velocity and acceleration are both vectors, they have the same direction if they are both positive or both negative. Otherwise, they have opposite directions.

Let's say that i am moving to the right having velocity 2m/s and positive constant acceleration 1m/s². This means that one second later my velocity will be 2m/s+1m/s= 3m/s. So my motion is accelerated.

Let's say that i am moving to the right having velocity 2m/s and negative constant acceleration -1m/s². This means that one second later my velocity will be 2m/s-1m/s= 1m/s. So we have a decelerated motion.
Let's say that i am moving to the left having velocity -2m/s and positive constant acceleration 1m/². This means that one second later my velocity will be -2m/s+1m/s= -1 m/s. So we have decelerated motion because the magnitude of my velocity has been decreased.
Let's say that i am moving to the left having velocity -2m/s and negative constant acceleration -1m/s². This means that one second later my velocity will be -2m/s-1m/s= -3 m/s.
So my motion is accelerated because the magnitude of my velocity has been increased.