equivalence

Etymology

It is borrowed from Middle French équivalence,^{[2][3][4][5][6]} from Medieval Latin aequivalentia,^[4][5][6][2] from Late Latin aequivalēns (“equivalent”), the present participle of aequivaleō (“to be equivalent”),^[5][6][2] which is formed from Latin aequus (“equal”) and valeō (“to be strong, be worth”), from Proto-Indo-European *wal- (“to be strong”).^[5] The Merriam-Webster Unabridged and Dictionary.com take the English word from both the Middle French and the Medieval Latin.^[2][3]

Earliest recorded meaning

The condition of being equivalent, equality of value, force or meaning: before 1542, in Wyatt's prologue to Psalm 130.^[4] The Merriam-Webster Unabridged dates it to about 1541,^[2] and the Shorter Oxford to the late Middle English period.^[7] The variant equivalency is recorded from the 1530s.^[5]

Semantic evolution

From the general sense of equal value or force, the word was taken up by 19th-century science: the doctrine that one kind of force turns into another of the same value (1867), equality of energy or effect in physics (1874), and in chemistry the doctrine that fixed quantities of different substances are equivalent in combination (1880).^[4] Russell's use of 1906 marks the countable sense, an instance of equivalence, especially in mathematics and linguistics,^[4] and in 1918 Eddington wrote of the principle of equivalence in the theory of relativity.^[4][7] A verb equivalence, to balance or counterweigh, was used by Browne in 1646;^[4] Johnson (1755) entered it with Browne's sentence as his only example.^[8]

Timeline

• 1530s – the variant form equivalency.^[5]
• before 1542 – equality of value, force or significance, in Wyatt.^[4] Etymonline dates it to the 1540s.^[5]
• 1646 – verb, to balance or counterweigh (obsolete), in Browne.^[4][8]
• 1867 – the doctrine that one force is transformed into another of equal value.^[4]
• 1874 – in physics, equality of energy or effect.^[4]
• 1880 – in chemistry, the doctrine of chemical equivalents.^[4]
• 1906 – an instance of equivalence, in Russell.^[4][7]
• 1918 – the principle of equivalence in general relativity, in Eddington.^[4]

Meanings

Noun

1. The state of being equivalent, equal in value, force or meaning; interchangeability: the equivalence of the two currencies.^[2][9][4]
2. An instance of being equivalent.^[7][4]
3. (logic, mathematics) The relation between two statements each of which implies the other; also the truth-function that is true when both statements are true or both false, the biconditional.^[9]
4. (geology) The state of having been formed at the same time, of rock strata.^[2]
5. (physics) principle of equivalence: in general relativity, the postulate that the effects of a gravitational field cannot be told apart by experiment from those of an accelerated frame of reference.^[7][4]

Word family

• bioequivalence
• nonequivalence
• equivalence relation
• equivalence class
• equivalence principle

Related words

• equilibrium
• equivalent
• equivalency
• equal
• value
• valence

References

1. ^ Wiktionary, the free dictionary, https://en.wiktionary.org
2. ^ a b c d e f g Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
3. ^ a b Dictionary.com Unabridged (2016), based on the Random House Unabridged Dictionary, New York: Random House
4. ^ 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
5. ^ a b c d e f g Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
6. ^ a b c Klein, Ernest. A Comprehensive Etymological Dictionary of the English Language. 2 vols. Amsterdam: Elsevier, 1966–1967.
7. ^ a b c d e Shorter Oxford English Dictionary on Historical Principles (2002), 5th ed., ed. William R. Trumble and Angus Stevenson, Oxford: Oxford University Press
8. ^ 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.
9. ^ a b Collins English Dictionary (2023), Glasgow: HarperCollins