adequacy

Etymology

It is formed from English adequate + -acy,^[2][3][4][5] with -acy as an abstract noun suffix.^[6] Adequate is from Latin adaequātus (“made equal”), the past participle of adaequō (“to make equal, to level”),^[2][6] from ad- and aequō (“to make level”), from aequus (“equal, even”).^[6]

Earliest recorded meaning

The state or quality of being adequate: 1701, in S. Parker's Sylva.^[2][3] Etymonline dates the word to 1794,^[6] Dictionary.com to 1800–10,^[4] and the Shorter Oxford to the early 19th century, noting that inadequacy is earlier.^[7]

Semantic evolution

The word was preceded by adequateness, recorded from 1650.^[2][6] Webster (1828) defined it as being equal, proportionate or sufficient, a sufficiency for a particular purpose.^[8] Count uses followed: an adequate amount or number (1790) and a capability or area in which a person is competent (1813).^[2]

Timeline

• 1701 – the state or quality of being adequate.^[2][3]
• 1790 – an adequate amount or number.^[2]
• 1813 – a capability, an area of competence.^[2]

Meanings

Noun

1. The quality or state of being adequate; sufficiency for a purpose: Inspectors questioned the adequacy of the safety checks.^[3][9][2]
2. An adequate amount or number.^[2]
3. An ability or area in which a person is competent.^[2]

Related words

• adequate
• adequateness
• inadequacy
• equal

References

1. ^ Wiktionary, the free dictionary, https://en.wiktionary.org
2. ^ a b c d e f g h i j k Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
3. ^ a b c d Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
4. ^ a b Dictionary.com Unabridged (2016), based on the Random House Unabridged Dictionary, New York: Random House
5. ^ Klein, Ernest. A Comprehensive Etymological Dictionary of the English Language. 2 vols. Amsterdam: Elsevier, 1966–1967.
6. ^ a b c d e Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
7. ^ Shorter Oxford English Dictionary on Historical Principles (2002), 5th ed., ed. William R. Trumble and Angus Stevenson, Oxford: Oxford University Press
8. ^ Webster, Noah (1828), An American Dictionary of the English Language, New York: S. Converse
9. ^ Stevenson, Angus, ed. (2010), Oxford Dictionary of English, 3rd ed., Oxford: Oxford University Press