Insanity, craziness or madness is a spectrum of behaviors characterized by certain abnormal mental or behavioral patterns. Insanity may manifest as violations of societal norms, including a person becoming a danger to themselves or others, though not all such acts are considered insanity. In modern usage insanity is most commonly encountered as an informal unscientific term denoting mental instability, or in the narrow legal context of the insanity defense. In the medical profession the term is now avoided in favor of diagnoses of specific mental disorders; the presence of delusions or hallucinations is broadly referred to as psychosis. When discussing mental illness in general terms, "psychopathology" is considered a preferred descriptor.

In English, the word "sane" derives from the Latin adjective sanus meaning "healthy". The phrase "mens sana in corpore sano" is often translated to mean a "healthy mind in a healthy body". From this perspective, insanity can be considered as poor health of the mind, not necessarily of the brain as an organ (although that can affect mental health), but rather refers to defective function of mental processes such as reasoning. Another Latin phrase related to our current concept of sanity is "compos mentis" (lit. "of composed mind"), and a euphemistic term for insanity is "non compos mentis". In law, mens rea means having had criminal intent, or a guilty mind, when the act (actus reus) was committed.

Coordinates: 51°32′N 0°05′E / 51.54°N 0.08°E / 51.54; 0.08

Barking is a suburban town in the London Borough of Barking and Dagenham, in East London, England. A retail and commercial centre situated in the west of the borough, it lies 9.1 miles (14.6 km) east of Charing Cross. The area is identified in the London Plan as one of 35 major centres in Greater London. Barking is an area of regeneration with two main centres of activity, Barking Town Centre and Barking Riverside.

Its name came from Anglo-Saxon Berecingas, meaning either "the settlement of the followers or descendants of a man called Bereca" or "the settlement by the birch trees".

"Barking", in English slang, is short for "barking mad". Barking is sometimes cited as the origin of the phrase. This is attributed to the alleged existence of a medieval insane asylum attached to Barking Abbey. However, the phrase is not medieval, and first appeared only in the 20th century. A more likely derivation is from comparing an insane person to a mad dog.