deleterious - Wiktionary, the free dictionary

• deletorious (now proscribed)

Borrowed (1640s, 1582 as deletorious) from Medieval Latin deleterius, deletorius, from Ancient Greek δηλητήριος (dēlētḗrios, “noxious, deleterious”), from δηλητήρ (dēlētḗr, “a destroyer”), from δηλέομαι (dēléomai, “I hurt, damage, spoil, waste”).^[1] Not related to delete.

• (Received Pronunciation) IPA^(key): /ˌdɛl.ɪˈtɪə̯.ɹi.əs/, /ˌdɪl.ɪˈtɪə̯.ɹi.əs/
• (US) IPA^(key): /ˌdɛ.ləˈtɪɹ.i.əs/
• Rhymes: -ɪəɹiəs

deleterious (comparative more deleterious, superlative most deleterious)

1. (formal) Harmful, often in a subtle or unexpected way.

   Synonyms: destructive, harmful, hurtful, injurious, noxious, pernicious; see also Thesaurus:harmful

   deleterious effects

   deleterious to someone's health

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

     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.

   • 2017 September, Jean M. Twenge, “Have Smartphones Destroyed a Generation?”, in The Atlantic‎^[1]:

     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.

2. (genetics) Having lower fitness.

   A deleterious mutation

• deleteriously
• deleteriousness

• “deleterious”, in OneLook Dictionary Search.
• “deleterious”, in Webster’s Revised Unabridged Dictionary, Springfield, Mass.: G. & C. Merriam, 1913, →OCLC.
• Douglas Harper (2001–2024) “deleterious”, in Online Etymology Dictionary.