cleavage

Etymology

It is formed from English cleave + -age, from the verb meaning to split.^{[2][3][4][5][6][7]}

Earliest recorded meaning

In mineralogy, the splitting of crystals and certain rocks along their lines of natural fissure, or the state of being so split: 1816, in Cleaveland's treatise on mineralogy and geology.^[2][4] Etymonline dates the mineralogical sense, the tendency of rocks or gems to break cleanly along such lines, to 1805.^[3]

Semantic evolution

The word stayed a technical term for most of the 19th century: in mineralogy for the arrangement in layers along which a substance splits (1830, in Herschel), in geology for the fissile structure of slate (1839, in Murchison), and in biology for cell division (1876).^[2] The general sense, the action of splitting or the state of being split, literal or figurative, is recorded from 1867, in Froude;^[2][3] it came to be used of the division of a party or of opinion.^[5] In the South African diamond trade a cleavage was a small broken diamond of more than one carat.^[8] The sense "the cleft between a woman's breasts as shown by a low neckline" is first recorded in 1946, in Time magazine, which explained it as a trade term of the Johnston Office, the Hollywood censors;^[2][3] Etymonline reports the tradition that it was first used by Joseph I. Breen of the Production Code Administration, of Jane Russell's costumes in The Outlaw.^[3] By analogy the word is now used of other such clefts, as between the buttocks.^[1]

Timeline

• 1805 – the tendency of rocks or gems to split along natural fissures.^[3]
• 1816 – the splitting of crystals and rocks along natural planes; the plane of such splitting.^[2][4]
• 1830 – in mineralogy, a layered structure along which a substance splits.^[2]
• 1839 – in geology, the fissile structure of slate and similar rocks.^[2]
• 1867 – any splitting or division, literal or figurative.^[2][3]
• 1876 – in biology, cell division.^[2]
• 1913 – in South Africa, a small broken diamond.^[8]
• 1946 – the cleft between a woman's breasts.^[2][3]

Meanings

Noun

1. The hollow between a woman's breasts, especially as shown by a low neckline.^[2][3][1]
2. The tendency of a crystal or rock to split along definite planes, giving smooth surfaces; also, such a splitting.^[4][9][2]
3. The direction or plane along which a crystal or rock splits.^[4][2]
4. The act of splitting; the state of being split; a division, as between groups or opinions: a deep cleavage within the party.^[9][5][2]
5. In biology, the series of cell divisions by which a fertilized egg becomes a blastula.^[9][10][2]
6. A fragment of a diamond obtained by splitting.^[10][8]

Related words

• cleave
• cleft
• cleaver

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 Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
3. ^ a b c d e f g h i Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
4. ^ a b c d e Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
5. ^ a b c Shorter Oxford English Dictionary on Historical Principles (2002), 5th ed., ed. William R. Trumble and Angus Stevenson, Oxford: Oxford University Press
6. ^ Dictionary.com Unabridged (2016), based on the Random House Unabridged Dictionary, New York: Random House
7. ^ Partridge, Eric (1966), Origins: A Short Etymological Dictionary of Modern English, 4th ed., London: Routledge & Kegan Paul
8. ^ a b c A Dictionary of South African English on Historical Principles, Dictionary Unit for South African English, https://dsae.co.za
9. ^ a b c The American Heritage Dictionary of the English Language (1992), 3rd ed., Boston: Houghton Mifflin
10. ^ a b Merriam-Webster's Collegiate Dictionary (2003), 11th ed., Springfield, Mass.: Merriam-Webster