deleterious

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UK/ˌdɛl.ɪˈtɪə̯.ɹi.əs/UK/ˌdɪl.ɪˈtɪə̯.ɹi.əs/US/ˌdɛ.ləˈtɪɹ.i.əs/

adjective

Harmful, often in a subtle or unexpected way.

“deleterious effects”

Less commonScrabble 12

Meanings

adjectivedeleterious (comparative more deleterious, superlative most deleterious)

comparative more deleterious · superlative most deleterious · alternative deletorious

  1. formalHarmful, often in a subtle or unexpected way.

    deleterious effects

    4 more examples

    deleterious to someone's health

    Or might it suffice him, that every wholesome growth should be converted into something deleterious and malignant at his touch?

    1850, Nathaniel Hawthorne, “chapter XV”, in The Scarlet Letter

    A trolleybus service was established by the London Passenger Transport Board between North Woolwich and Stratford on February 6, 1938, and had a deleterious effect on railway passenger traffic.

    1946 May and June, J. G. Holmes, “The North Woolwich Branch”, in Railway Magazine, page 176

    The advent of the smartphone and its cousin the tablet was followed quickly by hand-wringing about the deleterious effects of “screen time.” But the impact of these devices has not been fully appreciated, and goes far beyond the usual concerns about curtailed attention spans.

    2017 September, Jean M. Twenge, “Have Smartphones Destroyed a Generation?”, in The Atlantic

    Synonyms: destructive, harmful, hurtful, injurious, noxious, pernicious, harmful, damaging

  2. biologyHaving lower fitness.

    A deleterious mutation

Synonyms & antonyms

More synonyms by meaning

adjectiveharmful to living things

Synonym sets from Open English WordNet, CC BY 4.0.

Origin

  1. Ancient Greekδηλητήριος“noxious, deleterious”
  2. Englishdeleterious

Adapted borrowing (1640s; 1582 as deletorious) of New Latin dēlētērius, dēlētōrius + -ous, from Ancient Greek δηλητήριος (dēlētḗrios, “noxious, deleterious”), from δηλητήρ (dēlētḗr, “a destroyer”), from δηλέομαι (dēléomai, “I hurt, damage, spoil, waste”). Not related to delete or deleble. Doublet of deletery.

Full word history & related roots →

Translations

Bulgarian вреден
  • вреден (vreden)harmful
Catalan deleteri
  • deleteriharmful
Dutch schadelijk
  • schadelijkharmful
Finnish haitallinen, epäsuotuisa
  • haitallinenharmful
  • epäsuotuisaharmful
  • vahingollinenharmful
French délétère
  • délétèreharmful
German schädlich, gesundheitsschädlich
  • schädlichharmful
  • gesundheitsschädlichharmful
Greek βλαπτικός
  • βλαπτικός (vlaptikós)harmful
Italian deleterio
  • deleterioharmful
Korean 해로운
  • 해로운 (haeroun)harmful
Norwegian Bokmål skadelig, ødeleggende
  • skadeligharmful
  • ødeleggendeharmful
Polish szkodliwy
  • szkodliwyharmful
Portuguese deletério
  • deletérioharmful
Romanian deleter, vătămător
  • deleterharmful
  • vătămătorharmful
  • nocivharmful
  • dăunătorharmful
Russian вре́дный, вредоно́сный
  • вре́дный (vrédnyj)harmful
  • вредоно́сный (vredonósnyj)harmful
Scottish Gaelic sgriosail
  • sgriosailharmful
Spanish deletéreo
  • deletéreoharmful
Swedish menlig
  • menligharmful
Turkish olumsuz, zararlı
  • olumsuzharmful
  • zararlıharmful
Ukrainian шкідли́вий, згу́бний
  • шкідли́вий (škidlývyj)harmful
  • згу́бний (zhúbnyj)harmful

Rhymes & wordplay

Rhymes with deleterious

All rhymes →
Cite this entry
APA

deleterious. (n.d.). In WatkinsX Dictionary. Retrieved November 2, 2026, from https://dictionary.watkinsx.com/word/deleterious

MLA

“deleterious.” WatkinsX Dictionary, https://dictionary.watkinsx.com/word/deleterious. Accessed November 2, 2026.

Chicago

WatkinsX Dictionary, s.v. “deleterious,” accessed November 2, 2026, https://dictionary.watkinsx.com/word/deleterious.

Source: deleterious on Wiktionary, CC BY-SA 4.0.