impurity

Etymology

It is inherited from Middle English impurite,^[2][3][4] borrowed from Latin impūritās (“uncleanness”),^[2][3][4][5] used in Latin in a moral sense,^[5] from impūrus (“not pure, unclean”),^[5][3] from in- (“not”) and pūrus (“clean, pure”).^[6] The OED and Klein instead give French: impurité, recorded in the 15th century and now French impureté.^[7][6] The Shorter Oxford and the Oxford Dictionary of English allow either French or Latin.^[8][9] Barnhart takes the noun as formed in Middle English from impure and -ity, perhaps after the Middle French word.^[10] Etymonline conjectures that the Latin adjective goes back to Proto-Indo-European *peue- (“to purify, cleanse”).^[5]

Earliest recorded meaning

That which makes a person morally impure, moral uncleanness: about 1450, in a translation of Thomas à Kempis's De Imitatione Christi,^[7] where the Middle English Dictionary quotes "all maner impurite", translating Latin impūritās.^[2] Etymonline likewise dates the word to the mid-15th century.^[5] Barnhart has before 1500.^[10]

Semantic evolution

The word entered English as a moral term, like the Latin one,^[7][5] and the state of moral impurity or unchastity is recorded from 1548,^[7] after Etymonline's "fact or quality of being impure" of about 1500.^[5] Physical senses followed: foul matter and dirt in 1598,^[7] then in 1605 foreign admixture of an inferior kind, without reference to foulness.^[7] Johnson (1755) listed "want of sanctity", "act of unchastity" and "feculent admixture" in that order.^[11] The technical sense "impurity atom", an atom of dopant in a semiconductor, is recorded from 1931.^[7]

Timeline

• c. 1450 – moral uncleanness, or something that makes one morally impure.^[7][5]
• 1548 – the state of being morally impure, in Udall's translation of Erasmus.^[7]
• 1598 – the condition of containing foul matter; dirt.^[7]
• 1605 – foreign matter that detracts from purity.^[7]
• 1931 – an impurity atom in a semiconductor.^[7]

Meanings

Noun

1. The quality or state of being impure, especially of containing dirt or foreign matter.^[12][3][7]
2. Something that makes a substance impure; a contaminant: The smelter burns off most of the impurities in the ore.^[12][3][7]
3. Moral uncleanness or unchastity, or an immoral act or word.^[3][7][8]
4. (electronics) A small quantity of an element added to a pure semiconductor crystal to control its conductivity.^[12][7]

Related words

• impure
• pure
• purity

References

1. ^ Wiktionary, the free dictionary, https://en.wiktionary.org
2. ^ a b c Kurath, Hans; Kuhn, Sherman M.; Lewis, Robert E., eds. (1952–2001), Middle English Dictionary, Ann Arbor: University of Michigan Press; online edition ed. Frances McSparran et al. (2000–2018)
3. ^ a b c d e f Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
4. ^ a b Dictionary.com Unabridged (2016), based on the Random House Unabridged Dictionary, New York: Random House
5. ^ a b c d e f g h Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
6. ^ a b Klein, Ernest. A Comprehensive Etymological Dictionary of the English Language. 2 vols. Amsterdam: Elsevier, 1966–1967.
7. ^ a b c d e f g h i j k l m n o p Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
8. ^ a b Shorter Oxford English Dictionary on Historical Principles (2002), 5th ed., ed. William R. Trumble and Angus Stevenson, Oxford: Oxford University Press
9. ^ Stevenson, Angus, ed. (2010), Oxford Dictionary of English, 3rd ed., Oxford: Oxford University Press
10. ^ a b Barnhart, Robert K. (1988), The Barnhart Dictionary of Etymology
11. ^ Johnson, Samuel (1755), A Dictionary of the English Language, London; 4th ed. 1773; Johnson's Dictionary Online, ed. Beth Rapp Young et al.
12. ^ a b c Collins English Dictionary (2023), Glasgow: HarperCollins