incoherent

Etymology

It is formed from English in- + coherent,^{[2][3][4][5][6]} with the negative prefix.^[3] The OED compares French incohérent, which it finds only from the 18th century.^[2] The base adjective is from French cohérent, from Latin cohaerēns, the present participle of cohaereō (“to cohere”),^[3][2] formed from com- (“together”) and haereō (“to stick, adhere”).^[3]

Earliest recorded meaning

Of abstract things, made up of parts that do not fit together; lacking unity: before 1631, in a sermon of Donne.^[2] Merriam-Webster dates the word to 1626^[5] and Etymonline to the 1620s, of thought and language.^[3]

Semantic evolution

The word was first used of ideas, schemes and speech that lack logical connection (1632 for thought and language),^[2][3] and of things that cannot be brought together, incompatible (1643, in Milton).^[2] The physical sense, of matter whose parts do not stick together, is later: 1695 in the OED,^[2] the 1690s in Etymonline.^[3] Johnson (1755) gave both, "inconsistent" and "loose, not cohering".^[7] From 1803 it was said of a person whose speech is confused,^[2] and Merriam-Webster notes that this is usually through strong emotion.^[5] In physics it has described, since 1929, waves with no fixed phase relationship, such as incoherent light.^[2][8]

Timeline

• 1626 – lacking coherence.^[5] The OED's first example is from before 1631.^[2]
• 1632 – of thought or language, disconnected, rambling.^[2]
• 1643 – incompatible, unable to combine.^[2]
• 1695 – lacking physical cohesion; loose.^[2][3]
• 1803 – of a person, speaking or thinking incoherently.^[2]
• 1929 – physics, of waves without a stable phase relationship.^[2]

Meanings

Adjective

1. Of speech, writing or thought: unclear, disordered or lacking logical connection: an incoherent letter.^[8][5][2]
2. Unable to express oneself clearly, often because of strong emotion: He was incoherent with grief.^[8][5]
3. Lacking unity or consistency; made up of parts that do not fit together.^[5][4][2]
4. Lacking physical cohesion; loose: incoherent sand.^[5][2]
5. (physics) Of two or more waves: having no fixed phase relationship.^[8][2][4]

Word family

• incoherently
• incoherentness
• incoherency

Related words

• incoherence
• coherent
• cohere
• cohesion
• adhere

References

1. ^ a b 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 Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
3. ^ a b c d e f g h Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
4. ^ a b c Shorter Oxford English Dictionary on Historical Principles (2002), 5th ed., ed. William R. Trumble and Angus Stevenson, Oxford: Oxford University Press
5. ^ a b c d e f g h Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
6. ^ Dictionary.com Unabridged (2016), based on the Random House Unabridged Dictionary, New York: Random House
7. ^ Johnson, Samuel (1755), A Dictionary of the English Language, London; 4th ed. 1773; Johnson's Dictionary Online, ed. Beth Rapp Young et al.
8. ^ a b c d Collins English Dictionary (2023), Glasgow: HarperCollins