Pernicious Meaning: Definition, Examples and Word Forms

Pernicious (adjective). Pernicious means seriously harmful or damaging, often in a way that is difficult to notice at first.

Example: The pernicious rumour gradually damaged trust between the two teams.

Pronunciation guide: per-NISH-uhs. Capital letters show the stressed syllable.

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What does pernicious mean?

Pernicious is a strong, formal adjective. It says that something has a seriously damaging effect. The harm is often subtle or develops gradually, but the word does not require every harmful effect to be slow or secret.

Useful combinations include pernicious influence, pernicious effects, pernicious myth and pernicious consequences. The adjective normally communicates a negative judgment.

In an argument, support that judgment with an explanation. If you describe a rule as pernicious, tell the reader what damage it causes instead of relying on the force of the word alone.

Pernicious in a sentence

• The pernicious rumour made classmates distrust someone who had done nothing wrong.
• The report examined the pernicious effects of rewarding speed while ignoring accuracy.
• A pernicious myth in the story convinces the villagers that asking questions is disloyal.
• The new editor challenged a pernicious habit of publishing accusations without checking them.
• In the novel, the adviser exerts a pernicious influence on the young ruler.

Each sentence identifies a cause or context for the harm. For a minor inconvenience, a milder word such as unhelpful or annoying is usually more proportionate.

Perniciousness and perniciously

Perniciousness is the noun for the harmful quality: “The perniciousness of the rumour became clear when it divided the class.”

Perniciously is the adverb: “The rumour perniciously undermined their trust.” This is a formal construction; “The rumour seriously damaged their trust” is a plainer alternative.

Compare “a pernicious influence” with “the perniciousness of the influence.” After “a,” use an adjective plus a noun, not an adjective standing alone as an object.

Pernicious versus insidious and harmful

Harmful is a broad word for causing harm. Pernicious usually gives the criticism greater force. Insidious emphasises a danger that advances subtly or escapes notice. Something can be both pernicious and insidious, but the words stress different aspects.

Malevolent points to an intention or wish to cause harm. Pernicious describes a damaging effect and does not by itself prove intent. Beneficial offers a useful contrast when discussing effects.

For careful writing, state the action and its consequence: “The rule discouraged students from reporting mistakes.” Then decide whether “pernicious” is justified by the seriousness of that consequence.

Practise pernicious: three quick questions

Try each question before opening its answer. If a question asks you to write a sentence, your own correct example is welcome.

Question 1

Does pernicious mean mildly inconvenient or seriously harmful?

Question 2

Which word particularly stresses a danger developing unnoticed: insidious or beneficial?

Question 3

Complete: “The ___ of the false story became clear.” Pernicious or perniciousness?

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Compare these words next: Opaque meaning and practice and Ubiquitous meaning and practice.

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Dictionary reference: Merriam-Webster: Pernicious. The examples and practice questions on this page are written for English Skill Studio.