- 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) Light, delicate, and translucent; so fine in texture as to be nearly transparent
The diaphanous curtains billowed in the breeze, letting the morning light pour softly into the room.
Diaphanous comes from the Medieval Latin diaphanus, itself from the Greek diaphanes — from dia (“through”) + phainein (“to show” or “to appear”). It entered English in the early 17th century, originally used to describe fine fabrics and minerals that allowed light to pass through them visibly.