illness

noun

ill·​ness ˈil-nəs 

1

a

: sickness sense 2

b

: an unhealthy condition of body or mind

2

obsolete

a

: wickedness

b

: unpleasantness

Synonyms of illness

• disease
• ailment
• ill
• sickness
• fever

Examples of illness in a Sentence

Her body was not able to defend itself against illness.

Hundreds of soldiers died from illness and hunger.

He showed no signs of illness.

Scientists have not yet found a cure for this illness.

cancer, diabetes, and other illnesses

She died at the age of 60 after a brief illness.

Recent Examples on the Web

Although the first illnesses began in mid-May, the CDC didn’t notify the public or healthcare providers about the outbreak until July 14. — Blake Ellis, CNN Money, 20 July 2026

While multiple cooling towers have tested positive for Legionella bacteria, investigators have not determined which, if any, are responsible for the illnesses. — Anthony Thompson, USA Today, 19 July 2026

Cyclosporiasis has been sickening thousands of people across the country, particularly in Michigan, recently with an intestinal illness causing explosive diarrhea with severe stomach cramps, bloating, nausea, fatigue, and unintended weight loss. — Staff Report, Hartford Courant, 18 July 2026

Michigan, the state with the highest case count, has recorded more than 5,000 illnesses as of July 17. — Jaewon Kang, Fortune, 18 July 2026

Word History

First Known Use

circa 1500, in the meaning defined at sense 2a

Phrases Containing illness

• bipolar illness
• illness anxiety disorder
• manic-depressive illness
• mental illness

Rhymes for illness

• stillness

Kids Definition

illness

noun

ill·​ness ˈil-nəs 

1

: an unhealthy condition of body or mind

2

: sickness sense 2

Medical Definition

illness

noun

ill·​ness ˈil-nəs 

: an unhealthy condition of body or mind : sickness