triad

[ trahy-ad, -uh d ]
/ ˈtraɪ æd, -əd /

noun

a group of three, especially of three closely related persons or things.
Chemistry.
  1. an element, atom, or group having a valence of three.Compare monad(def 2), dyad(def 3).
  2. a group of three closely related compounds or elements, as isomers or halides.
Music. a chord of three tones, especially one consisting of a given tone with its major or minor third and its perfect, augmented, or diminished fifth.
(initial capital letter) Military. the three categories of strategic-nuclear-weapons delivery systems: bombers, land-based missiles, and missile-firing submarines.

Origin of triad

1540–50; < Latin triad- (stem of trias) < Greek triás See tri-, -ad1

Related forms

tri·ad·ic, adjectivetri·ad·ism, noun
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for triad

British Dictionary definitions for triad (1 of 2)

triad

/ (ˈtraɪæd) /

noun

a group of three; trio
chem an atom, element, group, or ion that has a valency of three
music a three-note chord consisting of a note and the third and fifth above it
an aphoristic literary form used in medieval Welsh and Irish literature
the US strategic nuclear force, consisting of intercontinental ballistic missiles, submarine-launched ballistic missiles, and bombers

Derived Forms

triadic, adjectivetriadism, noun

Word Origin for triad

C16: from Late Latin trias, from Greek; related to Greek treis three

British Dictionary definitions for triad (2 of 2)

Triad

/ (ˈtraɪæd) /

noun

any of several Chinese secret societies, esp one involved in criminal activities, such as drug trafficking
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Medicine definitions for triad

triad

[ trīăd′, -əd ]

n.

A collection of three things or symptoms having something in common.
The transverse tubule, and the terminal cisternae on each side of it, in a skeletal muscle fiber.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.