locus

Etymology

It is borrowed from Latin locus (“place, position, location; topic, subject”),^[2][3][4][5] from Old Latin stlocus, of unknown origin according to the OED and Etymonline.^[2][3] Klein derives it from Proto-Indo-European *st(h)el- (“to place”), the root of stall.^[6] The rhetorical sense "topic" follows Latin writers, who used the word for Ancient Greek τόπος (tópos).^[2][3] The legal sense is short for locus standi.^[2]

Earliest recorded meaning

The place where something is situated or happens: 1648, in R. Harris's Two Letters.^[2] Etymonline, Barnhart and Merriam-Webster date the word to 1715,^[3][7][8] and the Shorter Oxford to the early 18th century.^[4]

Semantic evolution

In mathematics, a locus is the figure made up of all points that satisfy a given condition; the OED finds this in 1675, in a letter of John Collins,^[2] while Barnhart dates it to Chambers's Cyclopaedia (1727–51) and Etymonline to about 1750.^[7][3] A rhetorical use for a topic or head of argument, after Latin, appears in 1753.^[2][4] The 19th century gave the legal use for locus standi, the right to be heard in court (1866),^[2][4] and the 20th century the genetic sense, the position of a gene on a chromosome (1913),^[2][4] and in psychology locus of control, where a person feels the control of their life lies (1953).^[2][4] In later use the word also names the perceived seat of something abstract, as in the locus of power.^[2][4]

Timeline

• 1648 – the place where something is situated or occurs.^[2] Etymonline, Barnhart and Merriam-Webster date the word to 1715.^[3][7][8]
• 1675 – in mathematics, the figure formed by all points satisfying a condition.^[2] Barnhart dates this sense to 1727–51, Etymonline to about 1750.^[7][3]
• 1753 – in rhetoric, a topic (obsolete).^[2]
• 1866 – in law, short for locus standi.^[2]
• 1913 – in genetics, the position of a gene on a chromosome.^[2]
• 1953 – locus of control, in psychology.^[2]

Meanings

Noun

1. A place or position, especially the place where something happens or is centred: the locus of the dispute.^[9][8][4][2]
2. (law) The place where an event of legal significance happened, used in legal phrases.^[9][8]
3. (mathematics) The set of all points whose positions satisfy one or more given conditions, such as a circle for the points at a fixed distance from a centre.^[9][8][2]
4. (genetics) The position of a particular gene on a chromosome.^[9][8][2]
5. (law) The right to be heard in a court; locus standi.^[2][4]
6. Short for locus classicus, the standard passage cited to illustrate a word or subject.^[8]
7. (obsolete) In rhetoric, a subject or topic.^[2][4]

Word family

• locus classicus
• locus coeruleus

Related words

• local
• locality
• localize
• locate
• location
• locator
• locale
• lieu
• milieu
• topos

Usage notes

The plural is usually loci,^[3][9][8] which Merriam-Webster records with three pronunciations, and it also gives a rarer plural loca.^[8] A slang locus, a drugged or stupefying drink, recorded from 1693 and of uncertain origin, perhaps from Spanish loco (“mad”), has its own entry in the OED, with a verb meaning to drug someone in order to rob or abduct them (1829–98).^[2][4][10]

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 r s t u v w Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
3. ^ a b c d e f g h Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
4. ^ a b c d e f g h i j k Shorter Oxford English Dictionary on Historical Principles (2002), 5th ed., ed. William R. Trumble and Angus Stevenson, Oxford: Oxford University Press
5. ^ Hoad, T. F., ed. (1986), The Concise Oxford Dictionary of English Etymology, Oxford: Clarendon Press
6. ^ Klein, Ernest. A Comprehensive Etymological Dictionary of the English Language. 2 vols. Amsterdam: Elsevier, 1966–1967.
7. ^ a b c d Barnhart, Robert K. (1988), The Barnhart Dictionary of Etymology
8. ^ a b c d e f g h i Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
9. ^ a b c d e Collins English Dictionary (2023), Glasgow: HarperCollins
10. ^ Green, Jonathon (2010), Green's Dictionary of Slang, London: Chambers; digital ed. 2016–, https://greensdictofslang.com