inconsistent

American  

[in-kuhn-sis-tuhnt] / ˌɪn kənˈsɪs tənt /

adjective

1. lacking in harmony between the different parts or elements; self-contradictory.

   an inconsistent story.

   Synonyms:

   incoherent

2. lacking agreement, as one thing with another or two or more things in relation to each other; at variance.

   a summary that is inconsistent with the previously stated facts.

   Synonyms:

   irreconcilable, discrepant

3. not consistent in principles, conduct, etc..

   He's so inconsistent we never know if he'll be kind or cruel.

4. acting at variance with professed principles.

5. Logic. incompatible.

---

inconsistent British  

/ ˌɪnkənˈsɪstənt /

adjective

1. lacking in consistency, agreement, or compatibility; at variance

2. containing contradictory elements

3. irregular or fickle in behaviour or mood

4. Also: incompatible.  maths (of two or more equations) not having one common set of values of the variables: x + 2 y = 5 and x + 2 y = 6 are inconsistent

5. logic (of a set of propositions) enabling an explicit contradiction to be validly derived

---

Synonym Usage

Inconsistent, incompatible, incongruous refer to things that are out of keeping with each other. That which is inconsistent involves variance, discrepancy, or even contradiction, especially from the point of view of truth, reason, or logic: His actions are inconsistent with his statements. Incompatible implies incapability of close association or harmonious relationship, as from differences of nature, character, temperament, and the like: actions incompatible with honesty of purpose; qualities that make two people incompatible. Something that is incongruous is inappropriate or out of keeping, often to the point of being ridiculous or absurd: Incongruous characters or situations frequently provide a basis for comedy.

Other Word Forms

• inconsistently
  adverb

Etymology

Origin of inconsistent

First recorded in 1640–50; in- ³ + consistent

Explanation

Inconsistent describes something that's varied or irregular. So if you're supposed to floss every day, but you only remember every now and then, your commitment to oral hygiene could be called inconsistent. The adjective inconsistent first came into use in the 1640’s, with the sense of “not agreeing in substance or form.” Broken down into its roots, in plus consistent, the word literally means "not consistent." Behavior, results in lab experiments, and your cooking skills could all be described as inconsistent if they are irregular, spotty, and hard to predict.

Example Sentences

See Examples For:

inconsistent

Patterson's team say they were inconsistent about a motive, starting the trial by saying they wouldn't argue a particular motive, but ending it by implying there was one.

From BBC ● Aug. 17, 2026

While stocks have generally trended higher across all periods, Kaeppel explained that returns during the unfavorable stretches have been far more volatile and inconsistent than what has been seen during the favorable periods.

From MarketWatch ● Aug. 11, 2026

Executives said McDonald's World Cup promotions had underperformed versus expectations, while suggesting that inconsistent implementation of value-oriented promotional deals was a bigger factor.

From Barron's ● Aug. 4, 2026

The team has seen so many certificates that it knows what to look for: fonts; inconsistent margins; the right official’s signature; a superimposed name of a student.

From The Wall Street Journal ● Aug. 4, 2026

Yet it’s always struck me how inconsistent these various authors have been in their use of large numbers.

From "Innumeracy: Mathematical Illiteracy and Its Consequences" by John Allen Paulos

Related Words

• conflicting
• contrary
• erratic
• illogical
• incompatible
• irreconcilable
• uncertain
• unpredictable