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pi

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Pronunciation

Etymology

It is the name of the Greek letter Ancient Greek πῖ (pî),[2][3] which is of Semitic origin.[2] Etymonline says it came from Phoenician, literally “little mouth”.[4] As the mathematical constant, π stands for περιφέρεια (periphéreia, “periphery”) (see periphery).[5][4][6][7]

Earliest recorded meaning

The name of the letter: the 15th century in Merriam-Webster.[2]

Semantic evolution

The Swiss mathematician Leonhard Euler used π for the ratio of a circle's circumference to its diameter in Latin in 1748,[4][5][3] and the use is found in English from 1841.[5][4] In electrical engineering a pi network is from 1924, and in physics and chemistry pi electrons and bonds from 1929.[3]

Timeline

  • 15th century – the letter pi.[2]
  • 1748 – π for the circle ratio (Euler, in Latin).[4][3]
  • 1841 – pi (mathematics, English).[5][4]
  • 1929 – pi electrons.[3]

Modern meaning

Noun

  1. The 16th letter of the Greek alphabet (Π, π).
  2. (mathematics) The ratio of the circumference of a circle to its diameter, a transcendental number of about 3.14159.

Word family

  • pion
  • pi meson

Usage notes

Pi, jumbled printing type, is a variant of pie.[4][3][8] An old school slang pi, pious or sanctimonious, is from about 1870.[3]

References

  1. ^ Jones, Daniel (2011), Cambridge English Pronouncing Dictionary, 18th ed., ed. Peter Roach, Jane Setter and John Esling, Cambridge: Cambridge University Press
  2. ^ a b c d Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
  3. ^ a b c d e f g Simpson, J. A.; Weiner, E. S. C., eds. (1989), The Oxford English Dictionary, 2nd ed., Oxford: Clarendon Press
  4. ^ a b c d e f g Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
  5. ^ a b c d Barnhart, Robert K. (1988), The Barnhart Dictionary of Etymology
  6. ^ Hoad, T. F., ed. (1986), The Concise Oxford Dictionary of English Etymology, Oxford: Clarendon Press
  7. ^ Collins English Dictionary (2023), Glasgow: HarperCollins
  8. ^ The American Heritage Dictionary of the English Language (1992), 3rd ed., Boston: Houghton Mifflin