A unit of equivalent dose. Rem relates the absorbed dose in human tissue to the effective biological damage of the radiation. Not all radiation has the same biological effect, even for the same amount of absorbed dose
U.S. Environmental Protection Agency, Radiation Glossary, Office of Radiation and Indoor Air Radiation Protection Division, Washington, DC, USA 2013. http://www.epa.gov/radiation/glossary/index.html#a , (Dzstr/ Rad Emr - Amer) {823}