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

Six claims that the stress of all this exacerbated his illness. — Owen Gleiberman, Variety, 17 Aug. 2026

Misfortune that brought back bad memories of last season’s mystery illness that caused Betts to lose nearly 20 pounds. — Mirjam Swanson, Los Angeles Times, 16 Aug. 2026

Khanna said medical costs remain a major source of financial insecurity, particularly for Americans diagnosed with serious illnesses. — Kiara Moore, The Washington Examiner, 16 Aug. 2026

Several iterations of the idea have since taken shape, expanding to refugees, students with intellectual and developmental disabilities, seniors with chronic illness. — Tess Kenny, Chicago Tribune, 15 Aug. 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