# mercurial

/mɝkˈjʊɹiəɫ/ (US) · /mɜːkjˈʊɹɪəl/ (UK) · CEFR C2 · Adjective

Source: https://englishreference.com/word/mercurial
Updated: 2026-05-25

## Definition

describing someone who changes their mind or mood very quickly. It can also describe something that is hard to control or predict because it moves so fast.

For teachers: characterised by sudden, unpredictable, or rapid changes in mood, temperament, or fortune. Historically associated with the planet Mercury and the element mercury due to their perceived volatility.

## Examples

- He is a mercurial character who changes his plans every hour.
- The politician's mercurial nature made it difficult for his advisors to predict how he would react to the new scandal.
- The poet's mercurial temperament is reflected in his body of work, which ranges from deeply somber elegies to lighthearted satires within a single volume.

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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.