illness
Americannoun
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poor health; sickness.
He grew up in an environment known for poverty, illness, and little opportunity for education.
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a specific sickness or disease, or an instance of such.
Please be as accurate as possible in listing your childhood illnesses.
- Synonyms:
- infirmity, affliction, ailment
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Obsolete. wickedness.
noun
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a disease or indisposition; sickness
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a state of ill health
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obsolete wickedness
Usage
What does illness mean? Illness is a state of poor health or sickness, as in I’ve had to miss a lot of work due to illness. The word illness is also commonly used to refer to a disease or instance of sickness. This sense of the word is often used when the type of disease is uncertain or unknown or when someone doesn’t want to specify what it is, as in They said that he is in the hospital with an illness, but they didn’t provide any further details. The word illness is based on the adjective ill, meaning sick. Example: The best way to avoid illness is to thoroughly wash your hands.
Etymology
Origin of illness
Compare meaning
How does illness compare to similar and commonly confused words? Explore the most common comparisons:
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.
Unwelcome as COVID’s emergence was, the sheer scale of its spread has vastly deepened science’s understanding of the ways that viruses can continue to affect a human body long after the initial illness has passed.
From Los Angeles Times • Jun. 15, 2026
In the 2010s, conversations about women, chronic illness, and the pain gap reached critical mass.
From Salon • Jun. 14, 2026
The British number one, who went into Queen's seeking to regain her form after a season disrupted by illness and injury, jumped for joy on sealing her victory as the crowd rose to applaud her.
From BBC • Jun. 13, 2026
Rather than selling mass-market step counters, they market premium products that synthesize biometrics like heart rate variability and skin temperature into actionable outputs: early illness warnings, recovery scores and training recommendations.
From The Wall Street Journal • Jun. 12, 2026
After Isaac left Monticello, a strange illness swept through Mulberry Row.
From "In the Shadow of Liberty" by Kenneth C. Davis
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
