Discretionary spending is the portion of the federal budget determined through the Congressional appropriations process. Approximately one-third of the budget is made up of discretionary spending -- a portion that has been shrinking since the 1960s.
Discretionary spending is evenly divided between two categories: defense and non-defense. Defense spending includes spending by the Department of Defense and the Department of Energy -- which has jurisdiction over nuclear weapons. Recent war spending is also included. Non-defense discretionary spending includes such categories as law enforcement, education, homeland security, environmental protection, transportation, disaster relief, medical research and foreign aid.