Final answer:
A carcinogen is any agent that directly increases the incidence of cancer. Most carcinogens are mutagens, and they can be biological, physical, or chemical in nature.
Step-by-step explanation:
A carcinogen is any agent that directly increases the incidence of cancer. Most, but not all carcinogens are mutagens. Carcinogens that do not directly damage DNA include substances that accelerate cell division, thereby leaving less opportunity for cell to repair induced mutations, or errors in replication. Carcinogens that act as mutagens may be biological, physical, or chemical in nature, although the term is most often used in relation to chemical substances.