side effects

Definition of side effect

side effect (side eh-FEKT): An effect of a drug or other type of treatment that is in addition to or beyond its desired effect. Side effects can be harmful or beneficial, and most go away on their own over time. Others may last past treatment or appear long after treatment has ended. Some common side effects of cancer treatment are nausea, vomiting, fatigue, pain, decreased blood cell counts, hair loss, and mouth sores.

Source: NCI Dictionary of Cancer Terms

side effect