Back means the rear of something.

Children should sit in the back of the car.

Dèyè vle di do yon bagay.

Timoun yo dwe chita dèyè machin nan.

If something is behind a thing or person, it is on the other side of them , or nearer their back rather than their front.

Behind bad luck comes good luck.

Si yon bagay dèyè yon bagay oswa yon moun, li pi pre do yo olye ke devan yo.

Dèyè move chans vini bon chans.

Behind in place or position.

Kids are lining up one after the other.

Plas oswa pozisyon dèyè.

Timoun yo fè liy youn dèyè lòt.

in a particular place after leaving or after others have moved on

Don\\'t leave me behind.

nan yon kote patikilye aprè yo fin kite oswa aprè yo fin deplase

Pa kite m dèyè.

at the back

Pierre put his luggage on the rear seat of the car.

Pierre mete sache li yo sou chèz dèye machin nan.

the fleshy part of the human body that you sit on

He sits on his backside.

pati nan kò imen an sou sa ou chita a

Li chita sou dèyè l.