Glossary

Ulceration: The formation of a break on the skin or on the surface of an organ. An ulcer forms when the surface cells die and are cast off. Ulcers may be associated with cancer and other diseases.

Ultraviolet (UV) radiation: Invisible rays from the sun. UV radiation can burn the skin and cause melanoma and other types of skin cancer. UV radiation that reaches the earth's surface is made up of two types of rays: UVA and UVB. UVA rays pass deeper into the skin and UVB rays are more likely to cause sunburn. Both kinds of radiation are believed to cause skin cancer and cause premature aging of the skin. People should use sunscreens that block or absorb both kinds of UV radiation.  

UV index: A daily measure of the strength of the sun's ultraviolet (UV) rays for a region.