A suntan is the darkening of skin that happens after spending time in the sun. When ultraviolet light from the sun hits your skin, your body responds by producing more melanin, a natural pigment that adds color and helps protect against sun damage. This process turns pale skin various shades of brown.

People often get suntans during summer activities like swimming, playing outside, or going to the beach. You might notice tan lines where your shirt or watch protected certain areas, leaving them lighter than the exposed skin around them.

While some people think a tan looks healthy, it's actually your skin's defense mechanism against something harmful. The same sun exposure that creates a tan can also cause sunburn, painful red skin that happens when you get too much sun too quickly. That's why dermatologists recommend wearing sunscreen: it blocks harmful rays while still letting you enjoy being outdoors.

The word can also be used as a verb, as in “I really tanned at the pool yesterday.” A suntan differs from a sunburn in that a tan develops gradually and doesn't hurt, while a sunburn appears quickly and can be quite painful.