Intelligence is the ability to understand from experience, acquire and retain knowledge, discern the difference between truth and error, right and wrong, and respond quickly and effectively to new situation.
At its basic physiological level intelligence correlates strongly with the speed that electrical impulses are transmitted by nerves. This speed of transmission is thought to form an overarching intelligence factor, often referred to as g or general mental ability (GMA). It is commonly accepted that there are many sub-types of intelligence which are strongly related to g but are still somewhat independent (e.g., verbal, numerical or computational intelligence). Disturbances and deformations of intelligence having a physiological cause are studied and treated with the combined resources of medicine and psychological counselling in psychiatry.
Military intelligence is knowledge of enemy forces, conditions in occupied territories, etc. See intelligence agency.