sigma

Etymology

It is borrowed from Latin sigma, from Ancient Greek σίγμα (sígma), the name of the eighteenth letter of the Greek alphabet.^[2][3][4][5] Etymonline, the American Heritage Dictionary, Merriam-Webster and Collins take the Greek name from a Semitic source related to the Hebrew letter name samekh, Etymonline as a metathesis of it;^[6][7][8][9] the American Heritage Dictionary and Partridge call the letter Phoenician in origin.^[7][10] Beekes, however, finds no evident Semitic model and the Hebrew name formally remote, and takes the name rather as a verbal noun from σίζω (sízō, “to hiss”),^[11] as Wiktionary does.^[1]

Earliest recorded meaning

The name of the Greek letter Σ, σ, ς, the equivalent of English S, whose uncial form is shaped like a C: Merriam-Webster dates it to 1584,^[8] the OED to 1607, in Edward Topsell's Historie of Foure-footed Beastes;^[2] the Shorter Oxford gives late Middle English.^[3]

Semantic evolution

In Greek the letter gave derivatives such as σιγματίζω (sigmatízō, “to write with a sigma”) and the adjective meaning sigma-shaped,^[11] the source of English sigmoid.^[10] In English the word was used from 1788, in Gibbon, of something shaped like an S or a C.^[2] As a symbol it was taken up by the sciences: in mathematics Σ marks a sum,^[9][8] in chemistry and physics σ has named electrons, orbitals and bonds with no angular momentum about the axis between two nuclei since 1929,^[2][3] in particle physics a triplet of hyperons since 1954,^[2][3][8] and in statistics a standard deviation, used as if it were a unit, since 1978.^[2][8] Merriam-Webster also records it for a millisecond and for a C-shaped spicule of a sponge.^[8]

Timeline

• 1584 – the Greek letter, in Merriam-Webster.^[8]
• 1607 – the Greek letter, in Topsell.^[2]
• 1788 – something shaped like an S or C, in Gibbon.^[2]
• 1929 – sigma electrons and orbitals, in chemistry and physics.^[2]
• 1954 – sigma particles, in particle physics.^[2]
• 1970 – sigma factor, in biochemistry.^[2]
• 1978 – a standard deviation, in statistics.^[2]

Meanings

Noun

1. The eighteenth letter of the Greek alphabet (Σ, σ, or ς at the end of a word), transliterated as S.^[9][8][2]
2. (mathematics) The sign Σ, showing that the quantities after it are to be added.^[9][8]
3. (statistics) The standard deviation, symbol σ.^[8][2]
4. (physics) A sigma particle, an unstable hyperon that occurs with positive, negative and neutral charge.^[8][2][3]
5. (chemistry) Used of an electron, orbital or bond with no angular momentum about the axis between two nuclei: a sigma bond.^[2][3]
6. A millisecond.^[8]
7. Something shaped like an S or a C.^[2]

Word family

• sigmate
• sigmoid
• sigmatism

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 Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
3. ^ 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
4. ^ Dictionary.com Unabridged (2016), based on the Random House Unabridged Dictionary, New York: Random House
5. ^ Weekley, Ernest (1921), An Etymological Dictionary of Modern English, London: John Murray
6. ^ Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
7. ^ a b The American Heritage Dictionary of the English Language (online 2024), 5th ed., Boston: Houghton Mifflin Harcourt
8. ^ a b c d e f g h i j k l Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
9. ^ a b c d Collins English Dictionary (2023), Glasgow: HarperCollins
10. ^ a b Partridge, Eric (1966), Origins: A Short Etymological Dictionary of Modern English, 4th ed., London: Routledge & Kegan Paul
11. ^ a b Beekes, Robert S. P. (2010), Etymological Dictionary of Greek, with the assistance of Lucien van Beek, Leiden Indo-European Etymological Dictionary Series 10, Leiden; Boston: Brill