Deleterious refers to something that causes harm or damage, especially to health or well-being.


US English

UK English

Part of Speech



Harmful, damaging, injurious, detrimental


Beneficial, advantageous, salutary, helpful

Word Forms

Part of Speech Words
Noun None
Verb None
Adjective deleterious
Adverb None

Example Sentences

  • Smoking is a deleterious habit that can cause lung cancer and other health problems.

  • The chemical spill had a deleterious effect on the local ecosystem, killing many fish and other aquatic life.

  • Prolonged exposure to loud noise can have deleterious effects on hearing.

  • The use of certain pesticides can have deleterious effects on the environment, including the depletion of soil nutrients.


The term “deleterious” is often used to describe something that is harmful, damaging, or detrimental in some way. It is frequently used in scientific or medical contexts to describe the negative effects of a substance, behavior, or condition. For example, a drug may be deemed deleterious if it has serious side effects or causes harm to the body, while an environmental pollutant may be considered deleterious if it harms wildlife or poses a threat to public health.

The word “deleterious” is derived from the Latin word “deleter”, which means “to injure” or “to destroy.” The suffix “-ious” is used to form adjectives and means “having the qualities of.” Therefore, the word “deleterious” literally means “having the qualities of causing injury or destruction.”

The prefix “de-” is often used to indicate negation or reversal, as in “deactivate” or “declassify.” In the case of “deleterious,” however, the prefix does not indicate negation but rather intensifies the meaning of the root word “leter,” which means “to destroy” or “to injure.”

Overall, the term “deleterious” is a strong and descriptive word that is often used to describe the harmful effects of something. Its negative connotations make it a useful word in many different contexts, from scientific research to environmental advocacy to public health campaigns. It is important to note, however, that the word “deleterious” should be used carefully and accurately, as it implies a high degree of harm or danger.