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

For casual listeners, there are other signs: Inconsistent drum patterns, bland lyrics, and a singer who never strays from the melody or lets rip on the final chorus.

From BBC • Jan. 16, 2026

Inconsistent definitions, data accuracy issues and poor national co-ordination risk undermining efforts to protect vulnerable children, His Majesty's Inspectorate of Constabulary and Fire and Rescue Services said in a progress report.

From BBC • Nov. 4, 2025

Focus groups in December and January reinforced the objections to Foundational and Inconsistent, according to a staff report.

From Los Angeles Times • Mar. 6, 2025

Inconsistent cell phone access isn’t uncommon among low-income Americans.

From Seattle Times • Dec. 18, 2023

His second and more important pamphlet, War Inconsistent with the Religion of Jesus Christ, was prepared for the press in 1812.

From War Inconsistent with the Religion of Jesus Christ by Dodge, David Low

Related Words

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