Calm down and Slow down

Calm down verb - To become still and orderly.

Slow down and calm down are semantically related In some cases you can use "Slow down" instead a verb "Calm down".

Slow down verb - Lose velocity; move more slowly.

Calm down and slow down are semantically related in relax topic. Sometimes you can use "Calm down" instead a verb "Slow down", if it concerns topics such as decrease, grow less or make less.