Conditioner is a hair care product that makes your hair softer, smoother, and easier to manage after you've washed it with shampoo. While shampoo cleans your hair by removing dirt and oil, it can leave hair feeling rough or tangled. Conditioner coats each strand with ingredients that smooth down the outer layer of the hair, like putting a protective finish on wood.

You typically apply conditioner after shampooing, letting it sit for a minute or two before rinsing it out. Some people with very dry or curly hair use a special leave-in conditioner that stays in their hair all day. Athletes with long hair often keep conditioner in their gym bags because chlorine from swimming pools or sweat from workouts can make hair feel dry and brittle.

An air conditioner improves the condition of air by cooling it down. A fabric conditioner (also called fabric softener) makes clothes feel softer, just like hair conditioner does for hair.