English Reference

Word

pernicious

Phoneticsper·ni·cious

US/pɝˈnɪʃəs/

UK/pɜːnˈɪʃəs/

Definition

adj. 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.

adj. 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.”

Examples

simple

“The pernicious effects of smoking are well known.”

contextual

“The spread of the pernicious rumor caused a lot of unnecessary panic among the local residents.”

complex

“The philosopher argued that the pernicious influence of wealth on the mind was the primary reason for the decline of the republic.”

Real-World Examples

“He said Arday had faced "an unacceptable public hounding and campaign of abuse", adding that he was a victim of "a pernicious public shaming that other people in his position simply wouldn't have faced".”
BBC News · 15 Aug 2026
“Air pollution in particular is a pernicious problem in the U.S.”
The Conversation · 31 Jul 2026

Etymology

From Middle English, from Old French pernicios, from Latin perniciōsus (“destructive”), from perniciēs (“destruction”), from per (“through”) + nex (“slaughter, death”).

Analyzable as pernīx ("swift") + -ious.

Etymology adapted from Wiktionary, available under CC BY-SA 4.0.

Collocations

pernicious public

This entry

Level
C1 · Advanced
Frequency
Occasional
Updated

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English Reference