gnomon

Etymology

It is borrowed from Latin gnōmōn,^{[2][3][4][5][6]} from Ancient Greek γνώμων (gnṓmōn, “inspector, indicator, pointer of a sundial, carpenter's square, literally one that discerns”).^[7][2][5][8] The OED treats it as a borrowing from Greek whose immediate source may have been Latin or French gnomon,^[7] and Hoad and the Shorter Oxford also name French.^[9][10] The Greek noun is from γιγνώσκω (gignṓskō, “to come to know, perceive, judge”),^[7][2][3][8] from Proto-Indo-European *ǵneh₃- (“to know”),^[1][2][4] and so is related to know.^[3][1] Klein connects it with γνώμη (gnṓmē, “mind, judgment, maxim”), the source of gnome, and with pathognomonic and physiognomy.^[11] According to Merriam-Webster's Book of Word Histories, norma (“carpenter's square”), the source of norm and normal, probably comes from the Greek word as well;^[12] Etymonline calls the Latin word of unknown origin and reports Klein's suggestion of a borrowing through Etruscan.^[2]

Earliest recorded meaning

An object that shows the time of day by the shadow it casts, especially the pin or triangular plate of a sundial: 1546, in T. Langley's translation of P. Vergil.^[7][3][5] Etymonline dates it to the 1540s, and notes that early English use sometimes turned the word into knowman by folk etymology.^[2]

Semantic evolution

The Greek word already meant the pointer of a sundial and a carpenter's square, and in the plural the teeth that show a horse's or mule's age.^[7][2] The geometers' sense, the part of a parallelogram left after a similar one is removed from a corner, is recorded from 1570 in Billingsley's translation of Euclid, or from the 1560s according to Etymonline,^[7][2] and it is named after the shape of a carpenter's square.^[9][8][1] The 17th century tried out several learned uses: a column for measuring the sun's meridian altitude (1625), the teeth that show a horse's age (1607, rendering the Greek plural), a rule of belief or action (1627), the Pythagoreans' name for an odd number (1660) and an L-shaped bar (1669).^[7] A jocular use for the nose runs from 1582, in Stanyhurst, to 1803.^[7][10] By 1755 Johnson knew only "the hand or pin of a dial",^[13] and only the sundial, the astronomical column and the geometrical figure have survived.^[7][5]

Timeline

• 1546 – the shadow-casting pin or plate of a sundial.^[7][3][5]
• 1570 – in geometry, what remains of a parallelogram after a similar one is taken from a corner.^[7] Etymonline dates this to the 1560s.^[2]
• 1582 – jocularly, the nose (obsolete by 1803).^[7]
• 1599 – other instruments serving as indicators (obsolete by 1755).^[7]
• 1607 – plural, the teeth that show a horse's age.^[7]
• 1625 – a column for observing the sun's meridian altitude.^[7]
• 1627 – a rule of belief or action (obsolete by 1698).^[7]
• 1660 – an odd number, among the Pythagoreans.^[7]
• 1669 – something shaped like a carpenter's square (obsolete by 1777).^[7]

Meanings

Noun

1. An object that shows the time by the position or length of its shadow, especially the pin or plate of a sundial.^{[14][4][5][7]}
2. A column or shaft formerly used to find the sun's meridian altitude.^[5][7]
3. In geometry, the figure left when a parallelogram is removed from one corner of a larger, similar one.^{[14][4][5][7]}
4. (obsolete, 1582–1803) Jocularly, the nose.^[7][10]
5. (obsolete, 1599–1755) An instrument or other thing serving as an indicator.^[7][10]
6. (obsolete, 1627–98) A rule or canon of belief or action.^[7][10]
7. (obsolete, 1669–1777) Something shaped like a carpenter's square; an L-shaped bar.^[7][10]

Word family

• gnomonic

Related words

• know
• gnome
• physiognomy
• pathognomonic
• norm
• normal

References

1. ^ a b c d e Wiktionary, the free dictionary, https://en.wiktionary.org
2. ^ a b c d e f g h i Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
3. ^ a b c d e Barnhart, Robert K. (1988), The Barnhart Dictionary of Etymology
4. ^ a b c d The American Heritage Dictionary of the English Language (online 2024), 5th ed., Boston: Houghton Mifflin Harcourt
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. ^ 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 Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
8. ^ a b c Weekley, Ernest (1921), An Etymological Dictionary of Modern English, London: John Murray
9. ^ a b Hoad, T. F., ed. (1986), The Concise Oxford Dictionary of English Etymology, Oxford: Clarendon Press
10. ^ 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
11. ^ Klein, Ernest. A Comprehensive Etymological Dictionary of the English Language. 2 vols. Amsterdam: Elsevier, 1966–1967.
12. ^ Merriam-Webster's Book of Word Histories, Springfield, Mass.: Merriam-Webster
13. ^ Johnson, Samuel (1755), A Dictionary of the English Language, London; 4th ed. 1773; Johnson's Dictionary Online, ed. Beth Rapp Young et al.
14. ^ a b Collins English Dictionary (2023), Glasgow: HarperCollins