concave

Etymology

It is inherited from Middle English concave,^[2][3] borrowed from Old French concave or directly borrowed from Latin concavus (“hollow, arched, vaulted, curved”),^{[4][5][6][7][8]} the Latin adjective being formed from com-, here perhaps an intensive prefix,^[4][3] and cavus (“hollow”),^[4][8][3] the source of cave,^[9][5] from Proto-Indo-European *keue- (“to swell; vault, hole”).^[4] The French word is recorded from the 14th century, in Oresme.^[8] The noun is from the Old French noun, itself from the adjective,^[5][8] or else an elliptical use of the English adjective,^[6] and the OED compares concava (“hollows”).^[8] The verb is formed from the adjective, according to the OED,^[8] or from Old French concaver or Latin concavō, according to the Shorter Oxford.^[6]

Earliest recorded meaning

As a noun, a hollow or cavity: before 1398, in Trevisa's translation of Bartholomew, according to Barnhart.^[5] As an adjective, having a cavity or recess: probably before 1425, in a translation of Guy de Chauliac, a wonde concaue.^[2][5] The OED, in an entry not fully revised, has the noun only from about 1541 and the adjective from about 1560.^[8]

Semantic evolution

The first adjectival sense was simply "hollow, having a cavity inside", as in As You Like It, where a man in love is "as concave as a covered goblet, or a worm-eaten nut";^[10][11] the OED records it until 1659.^[8] The geometrical sense, "curved like the inside of a circle or sphere", the reverse of convex, is recorded from 1594 and is the survivor,^[8] with lenses and mirrors as its special case from about 1560.^[8] Johnson (1755) gave it first, with the inner surface of an eggshell and the inner curve of an arch as his examples.^[10] The noun went through its own specialised uses: the vault of an arch or of the sky (1554, 1635), the bore of a gun (1595–1678), a concave lens or mirror (1632–1797), a card cut to be used in cheating (1825) and a part of a threshing machine (1874).^[8] Mathematicians have used the adjective for "not convex" since 1942.^[8]

Timeline

• before 1398 – noun, a hollow or cavity.^[5]
• probably before 1425 – adjective, having a cavity or recess, of a wound.^[2][5]
• 1554 – noun, a concave surface, a vault or arch.^[8]
• probably before 1560 – adjective, of glasses, lenses and mirrors.^[8]
• 1594 – adjective, curved like the inside of a circle or sphere.^[8]
• 1595 – noun, the bore of a gun (obsolete by 1678).^[8]
• 1632 – noun, a concave lens or mirror (obsolete by 1797).^[8]
• 1635 – noun, the vault of heaven.^[8]
• 1652 – verb, to make concave.^[8]
• 1825 – noun, a card cut for cheating.^[8]
• 1874 – noun, a concave part of a machine such as a thresher.^[8][11]
• 1942 – adjective, in mathematics, not convex.^[8]

Meanings

Adjective

1. Curving inward like the inside of a bowl; the opposite of convex: The dish has a shallow concave base.^[12][11][8]
2. (physics) Of a lens or mirror, having a surface curved like a section of the inside of a sphere.^[12][8]
3. (mathematics) Of a polygon, having an interior angle greater than 180°; of a figure or set, not convex.^[12][8]
4. (obsolete, 1560–1659) Having a hollow interior.^{[8][12][11][6]}

Noun

1. A concave surface or structure; a vault or arch, especially the vault of the sky.^[11][8][6]
2. A hollow or curved recess in a mass or surface.^[11][8]
3. A set of bars or teeth curved around the cylinder of a threshing machine.^[11][8]
4. (obsolete, 1595–1678) The bore of a gun.^[11][8]
5. (obsolete, 1632–1797) A concave lens or mirror.^[11][8]

Verb

1. To make concave.^[12][11][8]
2. To curve in a concave way.^[11]

Word family

• concavely
• concaveness
• biconcave
• planoconcave
• subconcave
• concavity

Related words

• cave
• cavity
• convex

Usage notes

The word is usually stressed on the first syllable, but the Shorter Oxford gives second-syllable stress as an option when it stands after the noun, and the OED notes that poets often stressed the noun that way.^[6][8]

References

1. ^ a b 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 The American Heritage Dictionary of the English Language (online 2024), 5th ed., Boston: Houghton Mifflin Harcourt
4. ^ a b c d Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
5. ^ a b c d e f g Barnhart, Robert K. (1988), The Barnhart Dictionary of Etymology
6. ^ a b c d e f Shorter Oxford English Dictionary on Historical Principles (2002), 5th ed., ed. William R. Trumble and Angus Stevenson, Oxford: Oxford University Press
7. ^ Hoad, T. F., ed. (1986), The Concise Oxford Dictionary of English Etymology, Oxford: Clarendon Press
8. ^ 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 32 33 Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
9. ^ Klein, Ernest. A Comprehensive Etymological Dictionary of the English Language. 2 vols. Amsterdam: Elsevier, 1966–1967.
10. ^ 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.
11. ^ a b c d e f g h i j k Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
12. ^ a b c d e Collins English Dictionary (2023), Glasgow: HarperCollins