- Today's Word
Deleterious
[del-uh-TEER-ee-us]
Definition
- (adjective) Harmful, damaging, or having a detrimental effect on someone’s health, well-being, or situation. It describes something that causes gradual or subtle harm, often in ways that might not be immediately obvious.
Example
The scientist’s research showed that lack of sleep has a deleterious effect on both mental performance and physical health, even if people don’t notice it right away.
Fun Fact
“Deleterious” comes from the Greek word “dēlētērios,” meaning “noxious” or “harmful,” which itself derives from “dēleisthai,” meaning “to hurt” or “to damage.” The word first appeared in English during the 1640s, primarily in medical texts discussing harmful substances or conditions. Interestingly, in ancient Greek medicine, physicians used this term specifically to describe poisons that worked slowly and imperceptibly, distinguishing them from acute toxins that caused immediate harm. This subtle distinction continues in modern usage, where “deleterious” often implies gradual or cumulative damage rather than sudden harm. The word gained broader use during the Industrial Revolution when scientists and reformers needed precise language to describe the harmful effects of various industrial practices on public health. Today, it’s frequently used in scientific, medical, and environmental contexts to describe subtle but significant negative impacts.
(adjective) Relentlessly stern and humorless in manner; gloomy and forbidding in appearance or disposition.
The dour headmaster presided over every assembly with the expression of someone who had personally witnessed the decline of civilization and held the students responsible.