Simply put, a dehumidifier is a unit that eliminates excessive humidity from the air. There are other definitions like the ones you find on Wikipedia or your own dictionary—a dehumidifier is a home appliance used to reduce the amount of humidity in the air (Wikipedia). There are many different dehumidifier units in the market today. A dehumidifier can also be used to get rid of musty smells and mold that may be growing in your house. They kind of work like air conditioners apart only that they may not necessarily cool the air.