triad

Etymology

It is borrowed from Late Latin trias (“the number three, a triad”),^{[2][3][4][5][6]} from Ancient Greek τριάς (triás, “the number three, a group of three”),^[4][7][5] from τρεῖς (treîs, “three”),^[3][4][7] which is related to three.^[4][8] Hoad, the Shorter Oxford and the Oxford Dictionary of English allow a borrowing from French triade as well,^[9][10][11] which the OED dates in French to 1564.^[5]

Earliest recorded meaning

A group or set of three: 1546, in the State Papers of Henry VIII.^[5][3] Etymonline dates the word to the 1540s, in the sense of a union or conjunction of three.^[4]

Semantic evolution

Johnson (1755) gave only "three united".^[12] From the 17th century the general sense was applied to particular groups: the number three in Pythagorean philosophy (1660), the Trinity (1661), after the Greek use of triás by early Christian writers, and a group of three gods or powers (before 1746).^[5] Scholars of Welsh literature used it from 1839 for a form of composition that arranges subjects or statements in threes.^[5] Technical senses followed: in music a chord of a note with its third and fifth, recorded from 1786 in the OED,^[5] while Etymonline dates it to 1801;^[4] in chemistry a trivalent element (1865); and in pathology a group of three symptoms (1899).^[5] From 1821 English used Triad Society for a Chinese secret society, translating its Chinese name, San Ho Hui, literally "three unite society", said to mean the union of Heaven, Earth and Man.^[5][11] Collins records the later sense of the American nuclear force of land-based missiles, submarine-launched missiles and bombers.^[13]

Timeline

• 1546 – a group or set of three.^[5][3]
• 1660 – the number three, in Pythagorean philosophy.^[5]
• 1661 – the Trinity.^[5]
• before 1746 – a group of three deities or powers.^[5]
• 1786 – in music, a chord of three notes.^[5] Etymonline dates this sense to 1801.^[4]
• 1821 – the Triad Society, a Chinese secret society.^[5]
• 1839 – a Welsh literary form arranged in threes.^[5]
• 1865 – in chemistry, a trivalent element or radical.^[5]
• 1899 – in pathology, a group of three symptoms.^[5]

Meanings

Noun

1. A group of three closely related people, things or ideas; a trio: a triad of virtues.^[13][8][5]
2. In music, a chord of three notes, a root with the third and fifth above it.^[13][8][5]
3. In chemistry, a trivalent atom, element or radical.^[13][8][5]
4. A short aphoristic form of medieval Welsh and Irish literature, grouping its statements in threes.^[13][8][5]
5. In medicine, a set of three symptoms or signs that occur together.^[8][5]
6. The United States' strategic nuclear force of intercontinental ballistic missiles, submarine-launched missiles and bombers.^[13]
7. Triad: any of several Chinese secret societies, especially one engaged in organized crime.^[13][5][11]

Word family

• triadic
• triadically
• triadism
• major triad
• minor triad

Related words

• three
• trio
• trinity
• triangle

References

1. ^ Wiktionary, the free dictionary, https://en.wiktionary.org
2. ^ Barnhart, Robert K., ed. (1995), The Barnhart Concise Dictionary of Etymology, New York: HarperCollins
3. ^ a b c d Barnhart, Robert K. (1988), The Barnhart Dictionary of Etymology
4. ^ a b c d e f g Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
5. ^ a b c d e f g h i j k l m n o p q r s t u v w x Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
6. ^ The American Heritage Dictionary of the English Language (online 2024), 5th ed., Boston: Houghton Mifflin Harcourt
7. ^ a b Klein, Ernest. A Comprehensive Etymological Dictionary of the English Language. 2 vols. Amsterdam: Elsevier, 1966–1967.
8. ^ a b c d e f Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
9. ^ Hoad, T. F., ed. (1986), The Concise Oxford Dictionary of English Etymology, Oxford: Clarendon Press
10. ^ Shorter Oxford English Dictionary on Historical Principles (2002), 5th ed., ed. William R. Trumble and Angus Stevenson, Oxford: Oxford University Press
11. ^ a b c Stevenson, Angus, ed. (2010), Oxford Dictionary of English, 3rd ed., Oxford: Oxford University Press
12. ^ Johnson, Samuel (1755), A Dictionary of the English Language, London; 4th ed. 1773; Johnson's Dictionary Online, ed. Beth Rapp Young et al.
13. ^ a b c d e f g Collins English Dictionary (2023), Glasgow: HarperCollins