# illogical

/ˌɪˈɫɑdʒɪkəɫ/ (US) · /ɪlˈɒdʒɪkəl/ (UK) · CEFR B2 · Adjective

Source: https://englishreference.com/word/illogical
Updated: 2026-05-08

## Definition

not making sense or not following clear thinking. You use this to describe an idea or action that does not have a good reason behind it.

For teachers: lacking sense or sound reasoning; contrary to the principles of logic. Often used to describe arguments, decisions, or behaviors that fail to follow a rational sequence.

## Examples

- It is illogical to buy a car if you cannot drive.
- The manager's decision to cut the marketing budget during a sales slump seemed completely illogical to the team.
- While the protagonist's actions may appear illogical at first glance, they are driven by a deep-seated emotional trauma that bypasses rational thought processes.

## Pitfalls

- Not "His argument was unlogical." but "His argument was illogical." — The correct prefix for 'logical' is 'il-', not 'un-'.

## Usage notes

- Often used predicatively after linking verbs like 'seem', 'sound', or 'be'.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.