To humidify means to add moisture to the air. When air gets too dry, especially during winter when heaters are running, a humidifier releases water vapor to make the air more comfortable to breathe. You might notice one humming in your room at night, sending out a gentle mist.

Dry air can make your throat scratchy, your skin itchy, and even cause nosebleeds. It can also damage wooden furniture and musical instruments like guitars or pianos, which need a certain amount of moisture to stay in good condition. That's why museums often carefully humidify their galleries to protect valuable objects.

The opposite is dehumidify: removing moisture from air that's too damp. Basements often need dehumidifiers because underground spaces tend to trap moisture, which can lead to musty smells and mold.