deleterious

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

adjectiveC2Rare in speech; mostly a word you read · #13,031 of 15,258mostly written

Deleterious means doing harm, often quietly and over time. A deleterious effect, deleterious to health, deleterious consequences.

It is the formal register of harm and nearly always takes to, which is why it belongs to reports and studies. The Greek behind it means noxious, from a word for a destroyer.

Definitions of deleterious

1adjectivedeleteriousDoing harm, often quietly and over time.C2
“Lack of sleep can have a deleterious effect on your memory.”

deleterious is a quality.

Remember it

DELETErious → it slowly DELETEs your health

It looks harmless, but every dose deletes a little more of your health, until there is nothing left to delete.

hooks ontodelete

Where it comes from

Greek deleterios means noxious, from deleter, a destroyer.

Ancient Greek
δηλητήριος — noxious, deleterious
English, today
deleterious

Built from

δηλητήρ · Ancient Greek — a destroyer
δηλέομαι · Ancient Greek — I hurt, damage, spoil, waste

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

Etymology from Wiktionary, CC BY-SA

Practise this word

deleterious in the wild

The neutral theory assumes that most mutations that are not deleterious are neutral rather than beneficial.
Neutral theory of molecular evolution
The majority of genetic mutations are neutral or deleterious; beneficial mutations are relatively rare.
Mutation–selection balance
In natural selection, negative selection or purifying selection is the selective removal of alleles that are deleterious.
Negative selection (natural selection)
On the deleterious effects produced by drinking tea and coffee in excessive quantities.
All about coffee· William H. Ukers

From Wikipedia, CC BY-SA 4.0. These sentences were written by other people about their own subjects; they are here to show the word at work, not as anybody’s opinion.

From Project Gutenberg, public domain. These sentences are from real books, shown to illustrate the word at work.

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