deleterious
- 1Causing harm or damage, often gradually or in ways not at first obvious; in genetics, lowering an organism's fitness.
Researchers found that long hours of screen time had a deleterious effect on children's sleep.
Even low levels of the chemical may prove deleterious to fish in the river.
UsageUsually a deleterious effect on something or deleterious to something; harmful is the everyday word.
Similarharmful, damaging, detrimental, injurious, adverse
Oppositebeneficial, harmless, salutary, benign
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Origin
The Greek root is dēléomai, meaning "I hurt, damage, spoil, waste." From it came dēlētḗr ("a destroyer") and then dēlētḗrios ("noxious, deleterious"). New Latin took this as dēlētērius or dēlētōrius, and English adapted it with -ous in the 1640s, after an earlier form deletorious in 1582. Despite appearances it is not related to delete, but it is a doublet of deletery.
Checked 1 Nov 2026 · 8 facts
- The Greek root is dēléomai, meaning “I hurt, damage, spoil, waste.” en.wiktionary.org
- Dēlētḗr derives from dēléomai and means “a destroyer.” en.wiktionary.org
- Dēlētḗrios derives from dēlētḗr and means “noxious, deleterious.” en.wiktionary.org
- The Greek word passed into New Latin as dēlētērius or dēlētōrius. en.wiktionary.org
- English adapted the Latin word with -ous in the 1640s. en.wiktionary.org
- The earlier English form deletorious is recorded in 1582. en.wiktionary.org
- Deleterious is not etymologically related to delete. en.wiktionary.org
- Deleterious is a doublet of deletery. en.wiktionary.org