irreversible

Etymology

It is formed from English ir- + reversible, with the assimilated form of the negative prefix in- "not, opposite of".^[2][3][4][5] Merriam-Webster analyses it as in- + reverse + -ible,^[6][7] and Johnson (1755) likewise derived it from the negative prefix and the verb.^[8] The OED notes that it is recorded a few years before reversible itself (1632).^[3] The base goes back through the verb reverse to Latin reversus (“turned back”), the past participle of revertō (“to turn back, return”).^[2]

Earliest recorded meaning

That cannot be undone, repealed or annulled, used of decrees and the like: 1629, in W. Prynne's Church of Englands Old Antithesis.^[3] Etymonline dates it to the 1620s,^[2] and Merriam-Webster to 1630.^[6]

Semantic evolution

The word was first used of decrees and sentences that cannot be revoked;^[2][3] Johnson (1755) defined it as "not to be recalled; not to be changed", quoting a sermon on an "eternal irreversible sentence".^[8][3] Of physical things, "that cannot be turned backwards, upside down or the other way", it is recorded from 1819 in C. Lamb^[3] (Etymonline has 1821).^[2] Later scientific uses followed: in physical chemistry, from 1900, of a colloid that cannot be turned back from a gel into a sol by reversing the treatment,^[3][6] and in chemistry, physics and thermodynamics of reactions and processes that run in one direction only.^[9][6] In medicine it describes permanent damage.^[10]

Timeline

• 1629 – that cannot be undone or revoked, of decrees and sentences.^[3][2]
• 1819 – that cannot be turned backwards, upside down or the other way.^[3]
• 1900 – in physical chemistry, of a colloid that cannot be changed back from a gel to a sol.^[3]

Meanings

Adjective

1. Impossible to reverse or undo; permanent: The flood caused irreversible harm to the old library.^[9][6][4]
2. Impossible to revoke or repeal; irrevocable: an irreversible ruling.^[9][6][3]
3. Impossible to turn back, about or upside down.^[6][3]
4. In chemistry and physics, able to change or proceed in one direction only: an irreversible reaction.^[9][6]
5. In thermodynamics, of a process passing through intermediate states that are not all in equilibrium.^[9]
6. Of a colloid, unable to be changed back from a gel to a sol by reversing the treatment.^[6][3]
7. In medicine, of damage, permanent.^[10]

Word family

• irreversibility
• irreversibly

Related words

• reversible
• reverse
• revert
• irrevocable

References

1. ^ a b Wiktionary, the free dictionary, https://en.wiktionary.org
2. ^ a b c d e f Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
3. ^ a b c d e f g h i j k l m Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
4. ^ a b Shorter Oxford English Dictionary on Historical Principles (2002), 5th ed., ed. William R. Trumble and Angus Stevenson, Oxford: Oxford University Press
5. ^ Dictionary.com Unabridged (2016), based on the Random House Unabridged Dictionary, New York: Random House
6. ^ a b c d e f g h i Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
7. ^ Gove, Philip Babcock, ed. (1961), Webster's Third New International Dictionary of the English Language, Unabridged, Springfield, Mass.: G. & C. Merriam
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 c d e Collins English Dictionary (2023), Glasgow: HarperCollins
10. ^ a b The Chambers Dictionary (2014), 13th ed., Edinburgh: Chambers