Definitions

infectious

[in-fek-shuhs] / ɪnˈfɛk ʃəs /

ADJECTIVE

catching, spreading

Synonyms

STRONGEST

contagious toxic virulent

WEAK

communicable contaminating corrupting defiling diseased epidemic infective mephitic miasmic noxious pestilent pestilential poisoning polluting transferable transmittable vitiating

Antonyms

STRONGEST

harmless nonpoisonous

WEAK

antiseptic germless non-infectious uncommunicable uncontagious

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

These included initiatives addressing pandemic preparedness and outbreak response, health security, and infectious disease treatment.

From Slate • Jun. 9, 2026

This points to methionine as a possible tool for infectious diseases and inflammatory conditions, especially in people with kidney disease, kidney failure, or those undergoing dialysis.

From Science Daily • Jun. 1, 2026

But the energy of the production is infectious.

From Los Angeles Times • May 30, 2026

The body of a dead Ebola victim is highly infectious and can lead to the virus spreading further when prepared for burial.

From BBC • May 25, 2026

There was only one way she could continue working with dangerous infectious agents.

From "The Hot Zone" by Richard Preston

Vocabulary lists containing infectious

"Romeo and Juliet" by William Shakespeare, Act V

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National Nurses Week: Common Medical Terms

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An American Plague

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