- a group of three, especially of three closely related persons or things.
- Chemistry.
- an element, atom, or group having a valence of three.
- a group of three closely related compounds or elements, as isomers or halides.
- 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.
- 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.
- a group of three; trio
- an atom, element, group, or ion that has a valency of three
- 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
- any of several Chinese secret societies, esp one involved in criminal activities, such as drug trafficking
