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

Gauff battled an apparent illness during the Madrid Open, even taking a medical timeout in the Round of 32 over the weekend. —Chantz Martin, FOXNews.com, 30 Apr. 2026

An infant’s accidental exposure to an infected child can mean serious illness, brain swelling and sometimes death. —Orlando Sentinel, The Orlando Sentinel, 29 Apr. 2026

Severe postpartum psychiatric illness is particularly dangerous in the first year, when the suicide risk is increased seventy-fold. —Literary Hub, 29 Apr. 2026

Some patients, particularly the younger ones, are coming in after using AI to diagnose their symptoms — or their parents, suggesting all kinds of misguided illnesses. —Cindy Krischer Goodman, Sun Sentinel, 29 Apr. 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