adjective per·ni·cious \pər-ˈni-shəs\

Definition of pernicious

  1. 1 :  highly injurious or destructive :  deadly

  2. 2 archaic :  wicked





Examples of pernicious in a sentence

  1. The notion that poll data are a legitimate form of news has to be one of the most pernicious tenets of late-twentieth-century American journalism … —Barbara Ehrenreich, Nation, 20 Nov. 1995

  2. The more it [the Papacy] took part in the temporal conflicts with consistently pernicious result, the more impotent among the monarchs it revealed itself … —Barbara W. Tuchman, The March of Folly, 1984

  3. At its most pernicious, paper entrepreneurialism involves little more than imposing losses on others for the sake of short-term profits for the firm. —Robert B. Reich, Atlantic, March 1983

  4. More pernicious still has been the acceptance of the author's controversial ideas by the general public.

  5. the pernicious effects of jealousy

  6. She thinks television has a pernicious influence on our children.

insidious, sinister, or pernicious?

Few would choose to be associated with people or things that are insidious, sinister, or pernicious; all three of these words have decidedly unpleasant meanings, each with its own particular shade of nastiness.

Insidious comes from a Latin word for “ambush” (insidiae), which is fitting, as this word often carries the meanings “deceitful,” “stealthy,” or “harmful in an imperceptible fashion.” The first two meanings may be applied to people or things (“an insidious enemy,” “an insidious plot”), while the last is usually applied to things (“insidious problems,” “insidious sexism”), in particular to the gradual progress of a disease (“an insidious malignancy”).

Sinister comes from a Latin word meaning “on the left side, unlucky, inauspicious.” Although it is commonly used today in the sense “evil” (“a sinister cult leader”; “a sinister plot”), it may also suggest an ominous foreshadowing of some unfavorable turn of events (“a sinister omen”).

Pernicious has largely stayed true to its etymological root, the Latin noun pernicies “ruin, destruction.” Its original meaning in English, “highly injurious or destructive,” usually applies to things (“pernicious apathy,” “pernicious effects”) and medical conditions (“pernicious fever,” pernicious anemia). When applied to people, pernicious means “wicked.”

Origin and Etymology of pernicious

Middle English, from Anglo-French, from Latin perniciosus, from pernicies destruction, from per- + nec-, nex violent death — more at noxious

First Known Use: 15th century

Synonym Discussion of pernicious

pernicious, baneful, noxious, deleterious, detrimental mean exceedingly harmful. pernicious implies irreparable harm done through evil or insidious corrupting or undermining the claim that pornography has a pernicious effect on society. baneful implies injury through poisoning or destroying the baneful notion that discipline destroys creativity. noxious applies to what is both offensive and injurious to the health of a body or mind noxious chemical fumes. deleterious applies to what has an often unsuspected harmful effect a diet found to have deleterious effects. detrimental implies obvious harmfulness to something specified the detrimental effects of excessive drinking.

PERNICIOUS Defined for English Language Learners


adjective per·ni·cious \pər-ˈni-shəs\

Definition of pernicious for English Language Learners

  • : causing great harm or damage often in a way that is not easily seen or noticed

PERNICIOUS Defined for Kids


adjective per·ni·cious \pər-ˈni-shəs\

Definition of pernicious for Students

  1. :  causing great damage or harm a pernicious disease a pernicious habit

Medical Dictionary


adjective per·ni·cious \pər-ˈnish-əs\

Medical Definition of pernicious

  1. :  highly injurious or destructive :  tending to a fatal issue :  deadly pernicious disease

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