triad

American  

[trahy-ad, -uhd] / ˈtraɪ æd, -əd /

noun

1. a group of three, especially of three closely related persons or things.

2. Chemistry.

   1. an element, atom, or group having a valence of three.

   2. a group of three closely related compounds or elements, as isomers or halides.

3. 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.

4. Military. Triad, the three categories of delivery systems for strategic nuclear weapons, namely bombers, land-based missiles, and missile-firing submarines.

   The report says this missile is required in order to sustain an effective air leg of the Triad.

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triad ¹ British  

/ ˈtraɪæd /

noun

1. a group of three; trio

2. chem an atom, element, group, or ion that has a valency of three

3. music a three-note chord consisting of a note and the third and fifth above it

4. an aphoristic literary form used in medieval Welsh and Irish literature

5. the US strategic nuclear force, consisting of intercontinental ballistic missiles, submarine-launched ballistic missiles, and bombers

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Triad ² British  

/ ˈtraɪæd /

noun

1. any of several Chinese secret societies, esp one involved in criminal activities, such as drug trafficking

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Other Word Forms

• triadic adjective
• triadism noun

Etymology

Origin of triad

First recorded in 1540–50; from Latin triad- (stem of trias ), from Greek triás; see tri-, -ad ¹

Explanation

A triad is three things or people considered as one unit. A triad is a trio. A triangle is a shape with three sides. Similarly, a triad is a set of three things or people. To be a triad, three individual parts must also be considered a unit. A band with three members is a triad. A business with three divisions is a triad. A family with three members is a triad. A book with three volumes is a triad (usually called a trilogy). Triads are also called threesomes and trios.

Example Sentences

For the first time it publicly confirmed Beijing's "nuclear triad" of air, submarine and land capabilities.

From Barron's • Feb. 24, 2026

This will provide needed targeting flexibility and increase the value of the most ready and responsive leg of our triad.

From The Wall Street Journal • Feb. 15, 2026

Artists, mass media, infrastructure — the thriving triad was extraordinary to watch erupt.

From Los Angeles Times • Dec. 1, 2025

These matching maps round out a triad of evidence that suggests excess gamma rays in the center of the Milky Way could originate with dark matter.

From Science Daily • Oct. 18, 2025

Just as we might call Dunstaple’s contemporary Geoffrey Chaucer the father of English literature, so we should call John Dunstaple the father of the triad, and therefore of the Western harmonic system.

From "The Story of Music" by Howard Goodall

Related Words

• triumvirate