Other forms: conditioners
The job of a conditioner is to make something soft. If you use conditioner after you shampoo your hair, it will feel smoother and softer.
Hair conditioner is just one kind of conditioner — you might also treat your laundry with conditioner, softening your clothes, or your water with a conditioner that improves its quality. Another kind of conditioner is one that gets you physically into condition, or fitness. This might be an exercise or a teacher or trainer who instructs you in doing the exercise. Conditioner comes from the Old French condicion, "state or behavior," from the Latin condicionem, "situation."