# pernicious

/pɝˈnɪʃəs/ (US) · /pɜːnˈɪʃəs/ (UK) · CEFR C1 · Adjective

Source: https://englishreference.com/word/pernicious
Updated: 2026-05-20

## Definition

causing great harm or damage. You use this to describe things that are very bad for you, like a bad habit or a dangerous idea.

For teachers: causing or likely to cause great harm or damage. Often used to describe ideas, habits, or substances that have a slow but destructive effect.

## Examples

- The pernicious effects of smoking are well known.
- The spread of the pernicious rumor caused a lot of unnecessary panic among the local residents.
- The philosopher argued that the pernicious influence of wealth on the mind was the primary reason for the decline of the republic.

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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.