Triad

A triad, a group of three, may refer to:
 * Triad (symbol), Pythagorean symbol for the number three
 * Triplism in religion and mythology
 * Welsh Triads, collections of Medieval Welsh legend and history
 * Triad (music), set of three notes, most commonly forming a diatonic tertian chord
 * Triad (relationship), term for a relationship between three people
 * Triad (sociology), term for a group of three people as a unit of study

Medicine
In medicine, a triad often refers to three symptoms of a syndrome.


 * Triad (anatomy), structure in skeletal muscles, formed by a T tubule surrounded by sarcoplasmic reticulum
 * Catalytic triad, biochemical term for three amino acid residues found within some proteases
 * Beck's triad (cardiology), three typical symptoms of cardiac tamponade
 * Beck's cognitive triad, three types of negative thought present in depression
 * Charcot's triad, either of two sets of clinical signs, relating to multiple sclerosis or ascending cholangitis
 * Cushing's triad, a set of three signs showed by patients with head injuries
 * Dieulafoy's triad, a classic sign of acute appendicitis
 * Female athlete triad, three symptoms of low energy availability in female athletes
 * Hutchinson's triad, a common pattern of presentation for congenital syphilis
 * Meckler's triad, used to diagnose Boerhaave syndrome
 * Virchow's triad, a set of three signs attributed to Rudolf Virchow describing the pathogenesis of venous thrombosis
 * Whipple's triad, a set of three conditions proving hypoglycemia as the cause of a person's symptoms
 * MacDonald triad, three childhood traits that are associated with anti-social personality disorder

Organizations, brands and products

 * Triad (environmental science), management system for environmental cleanup
 * Triad (underground societies), Chinese organized crime groups
 * Triad Demand, UK electrical power demand measurement

Placenames

 * The Piedmont Triad, North Carolina, USA region

Computing

 * Triad (computers), group of three phosphor dots used in some computer monitors
 * Triad C64, Commodore 64 cracking group
 * Rise of the Triad, computer game

Popular culture

 * Triad (Battlestar Galactica), fictional ball sport
 * The Triad (Charmed), fictional group of three powerful demons
 * Triiad, a fictional alien species from the television series Hypernauts
 * Triad (superhero), alias of fictional DC Comics super hero Triplicate Girl
 * Triad (David Crosby song), a 1967 song by David Crosby, with versions recorded by Jefferson Airplane on Crown of Creation, by Crosby, Stills Nash & Young on Four Way Street, and by the Byrds on The Notorious Byrd Brothers
 * Triad (album), a 1976 album by Spontaneous Combustion.
 * Triad (Tool song), a song by Tool from their 2001 album Lateralus
 * The Hong Kong Triad (Thievery Corporation song), a song by Thievery Corporation from their 2000 album The Mirror Conspiracy