quaternary

Etymology

It is borrowed from Latin quaternārius (“containing or consisting of four”),^[2][3][4][5] which in post-classical Latin was also a noun for the number four, from the late 2nd or early 3rd century in Tertullian.^[2] The Latin adjective is formed from quaternī (“four each, a set of four”) and the suffix -ārius;^[2][6][7] quaternī is from quater (“four times”), related to quattuor (“four”),^[5][3][8][7] from Proto-Indo-European *kwetwer- (“four”).^[5][3] The OED compares Middle French quaternaire, a set of four, from the 16th century.^[2] The geological sense follows French quaternaire, proposed by the geologist J. Desnoyers in 1829 as a name for the fourth great epoch of geological time.^[2][5]

Earliest recorded meaning

The number four: about 1450, in The Art of Nombryng, an early arithmetic.^[2][4] Etymonline gives the adjective, consisting of four parts, from the early 15th century,^[5] but the OED and Barnhart first record the adjective in 1605.^[2][4]

Semantic evolution

The noun first meant the number four, a sense now obsolete,^[2][7] and Johnson (1755) defined it only so, with a quotation from Boyle on "the quaternary of elements".^[9] It then came to mean a set of four, and in medicine from 1597 to 1752 a period of four days in the course of a fever.^[2] The adjective, consisting of four parts or associated with the number four, followed in 1605.^[2][4] In the 19th century it was given the geological sense that matched tertiary: the Quaternary is the latest period of the Earth's history, comprising the Pleistocene and Holocene.^[8][2][10] The OED dates the geological adjective to 1840 and the noun to 1870,^[2] while Etymonline dates the capitalised geological term to 1843 and notes that not all geologists accepted it, since the period is far shorter than the earlier ones.^[5] Chemistry adopted it in 1871 for a compound, especially of ammonium, whose central atom forms four bonds to organic groups,^[2][7] and in 1961 J. Gottman used it for the sector of the economy that provides intellectual and information services.^[2]

Timeline

• c. 1450 – noun, the number four; later a set of four.^[2][4]
• 1597 – a period of four days in a fever (obsolete by 1752).^[2]
• 1605 – adjective, consisting of four parts.^[2][4][6]
• 1840 – adjective, of the latest geological period.^[2]
• 1851 – fourth in order or rank.^[2]
• 1870 – noun, the Quaternary period.^[2]
• 1871 – in chemistry, of a compound whose central atom forms four bonds to organic groups.^[2]
• 1961 – of the sector of the economy concerned with intellectual and information services.^[2]

Meanings

Adjective

1. Consisting of four parts or members, or arranged in fours: a quaternary scheme of classification.^[10][6][2]
2. Fourth in order or rank.^[10][6][2]
3. (geology) Usually capitalised: of or relating to the most recent period of geological time, which followed the Tertiary and includes the Pleistocene and Holocene epochs.^[10][6][2]
4. (chemistry) Containing an atom bound to four other atoms or groups, as in a quaternary ammonium compound.^[10][2][7]
5. (mathematics) Having four variables.^[10]
6. Of the sector of the economy concerned with intellectual and information services.^[2]

Noun

1. A group or set of four.^[6][10][2]
2. Usually capitalised: the Quaternary period, or the rocks formed during it.^[10][6][2]
3. (chemistry) A quaternary ammonium compound, especially one used as a disinfectant.^[2][7]
4. (obsolete) The number four.^[2][7][9]

Related words

• quaternion
• quatern
• quatrain
• quire
• quarter
• four
• tertiary
• ternary

References

1. ^ a b c Wiktionary, the free dictionary, https://en.wiktionary.org
2. ^ a b c d e f g h i j k l m n o p q r s t u v w x y z 27 28 29 30 31 Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
3. ^ a b c The American Heritage Dictionary of the English Language (online 2024), 5th ed., Boston: Houghton Mifflin Harcourt
4. ^ a b c d e f Barnhart, Robert K. (1988), The Barnhart Dictionary of Etymology
5. ^ a b c d e f Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
6. ^ a b c d e f g Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
7. ^ a b c d e f g Shorter Oxford English Dictionary on Historical Principles (2002), 5th ed., ed. William R. Trumble and Angus Stevenson, Oxford: Oxford University Press
8. ^ a b Hoad, T. F., ed. (1986), The Concise Oxford Dictionary of English Etymology, Oxford: Clarendon Press
9. ^ a b Johnson, Samuel (1755), A Dictionary of the English Language, London; 4th ed. 1773; Johnson's Dictionary Online, ed. Beth Rapp Young et al.
10. ^ a b c d e f g h Collins English Dictionary (2023), Glasgow: HarperCollins