inconsistent

Etymology

It was formed from English in- + consistent in English, with the negative prefix meaning "not".^[2][3][4][5] The OED compares inconsistant.^[2] Johnson (1755) explained it the same way.^[6]

Earliest recorded meaning

Of one thing compared with another, not agreeing with it in substance, spirit or form; at variance, incompatible, usually followed by with: 1646, in Sir Thomas Browne's Pseudodoxia Epidemica.^[2] Merriam-Webster gives 1620 and Dictionary.com 1640–50;^[4][7] Etymonline dates "not agreeing in substance or form" to the 1640s.^[3]

Semantic evolution

Of two or more things in relation to each other it is recorded from 1656,^[2] and of a single thing that contradicts itself from 1651, in Richard Baxter;^[2] Etymonline dates the sense "self-contradictory" to the 1650s.^[3] It was applied to people who act against their own principles or earlier behaviour from 1709.^[2] A rare sense "without firmness or consistence", of a substance, is recorded from 1677 and is now archaic.^[2] From 1690 there was also a church use, of a benefice that could not be held together with a fellowship.^[2] Johnson (1755) defined it as incompatible, unsuitable or incongruous.^[6] The technical senses in mathematics, of equations with no common solution, and in logic, of propositions from which a contradiction can be derived, are recorded in modern dictionaries.^[8]

Timeline

• 1620 – Merriam-Webster's first date.^[4]
• 1646 – at variance or incompatible with something.^[2]
• 1651 – self-contradictory.^[2][3]
• 1652 – noun, inconsistent things.^[2]
• 1656 – of two or more things, incompatible with each other.^[2]
• 1677 – of a substance, without firmness (rare).^[2]
• 1709 – of a person, not consistent in thought or action.^[2]

Modern meaning

Adjective

1. Not in agreement or harmony with something; incompatible, at variance, usually followed by with: The evidence was inconsistent with his story.
2. Containing parts that contradict each other; self-contradictory.
3. Not staying the same in quality, behaviour or mood; erratic or fickle: The team's form has been inconsistent all season.
4. (mathematics) Of equations, having no common set of values that satisfies them all.
5. (logic) Of a set of propositions, allowing a contradiction to be validly derived from them.

Word family

• inconsistently

Related words

• inconsistency
• consistent
• incongruous

Usage notes

Dictionary.com distinguishes inconsistent, incompatible and incongruous: inconsistent implies a discrepancy or contradiction, especially in terms of truth, reason or logic.^[7] In Northamptonshire and Huntingdonshire dialect inconsistent meant reprehensible, and in southern Worcestershire to be inconsistent meant to have a child before marriage.^[9]

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 Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
3. ^ a b c d Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
4. ^ a b c Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
5. ^ Shorter Oxford English Dictionary on Historical Principles (2002), 5th ed., ed. William R. Trumble and Angus Stevenson, Oxford: Oxford University Press
6. ^ 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.
7. ^ a b Dictionary.com Unabridged (2016), based on the Random House Unabridged Dictionary, New York: Random House
8. ^ Collins English Dictionary (2023), Glasgow: HarperCollins
9. ^ Wright, Joseph, ed. (1898–1905), The English Dialect Dictionary, 6 vols., Oxford: Henry Frowde; via EDD Online 4.0, University of Innsbruck (CC BY 4.0)