reciprocal

Etymology

It is borrowed from Latin reciprocus (“returning the same way, alternating”) with the suffix -al.^{[2][3][4][5][6]} The Latin adjective is explained as *recoprocos, from *recos (“turning backward”), formed on re- (“back”), and *procos (“turning forward”), formed on pro- (“forward”);^[3][7][8][5] so it first meant "going backward and forward".^[8] Klein relates the second element to procul (“far off”).^[8][9] Barnhart adds that attempts to take it further back into Indo-European have produced no convincing explanation.^[4] English had earlier reciproque, from Middle French reciproque (1532), and Barnhart suggests that reciprocal was a deliberate Latinate replacement for it;^[4][2] the OED notes that the adverb reciprocally is recorded slightly earlier.^[2]

Earliest recorded meaning

Given or done in return, answering: 1567, in G. Fenton's translation of Bandello.^[2][5] Barnhart and Etymonline date the word to 1570, Barnhart for the sense "inversely related",^[4][3] which the OED finds the same year in Billingsley's translation of Euclid.^[2]

Semantic evolution

The sense "felt or shared by both sides, mutual" appears in 1578 in Lyly's Euphues,^[2] or 1579 in Barnhart,^[4] and that of something exchanged between two parties in 1608, in Shakespeare's King Lear.^[2] From the 1590s the word also described movement backward and forward, later chiefly in mechanics;^[2][3] for this, the forms reciprocating, reciprocative and reciprocatory were also tried.^[3] The sense "interchangeable, equivalent in meaning" was used from 1616 to 1733,^[2] and Johnson (1755) still gave "mutually interchangeable" among its senses, after "alternate" and "mutual".^[10] In grammar it came to mean reflexive in the 17th century,^[7] and today names pronouns such as each other.^[11] The mathematical sense, of a quantity whose product with another is one, goes back to Billingsley's Euclid (1570).^[2][4]

Timeline

• 1567 – given or done in return.^[2][5]
• 1570 – mathematics, inversely related; also as a noun.^[2][4]
• 1578 – existing on both sides, mutual.^[2]
• 1594 – moving backward and forward alternately.^[2][3]
• 1608 – exchanged by two parties.^[2]
• 1616 – interchangeable, equivalent (obsolete by 1733).^[2]
• 1632 – opposite, inversely corresponding.^[2]
• 1902 – physics, of units that measure the reciprocals of standard quantities.^[2]

Meanings

Adjective

1. Given, felt or done by each of two parties to the other; mutual: a reciprocal trade agreement.^[11][2]
2. Given or done in return: She helped him, expecting a reciprocal favour.^[11][2]
3. (grammar) Of a pronoun or verb: expressing an action that each subject does to the other, as each other.^[11]
4. (mathematics) Of a quantity: related to another so that their product is one.^[11][2]
5. Inversely related; opposite.^[5][2]
6. (nautical) Of a course or bearing: differing by 180 degrees from another.^[11]
7. (obsolete, 1616–1733) Interchangeable; equivalent in meaning.^[2][10]

Noun

1. Something that is reciprocal to something else.^[5][4]
2. (mathematics) A number that gives one when multiplied by a given number: The reciprocal of 5 is 1/5.^[5][4]

Word family

• reciprocality
• reciprocally
• nonreciprocal
• unreciprocal
• reciprocal pronoun

Related words

• reciprocity
• reciprocate
• reciproque

References

1. ^ 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 Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
4. ^ a b c d e f g h i Barnhart, Robert K. (1988), The Barnhart Dictionary of Etymology
5. ^ a b c d e f g Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
6. ^ Stevenson, Angus, ed. (2010), Oxford Dictionary of English, 3rd ed., Oxford: Oxford University Press
7. ^ a b Hoad, T. F., ed. (1986), The Concise Oxford Dictionary of English Etymology, Oxford: Clarendon Press
8. ^ a b c Klein, Ernest. A Comprehensive Etymological Dictionary of the English Language. 2 vols. Amsterdam: Elsevier, 1966–1967.
9. ^ Skeat, Walter W. (1911), A Concise Etymological Dictionary of the English Language, new ed., Oxford: Clarendon Press
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 Collins English Dictionary (2023), Glasgow: HarperCollins