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

According to Billboard, Hall's condition came to light as his illness forced him to postpone 16 Hall & Oates tour dates in the summer of 2005. — Amaris Encinas, USA Today, 25 June 2026

Authors on the study found that COVID vaccines were roughly 55% effective in preventing hospitalizations associated with the illness and about 50% effective in decreasing trips to emergency rooms or urgent care facilities. — Rachel Raposas, PEOPLE, 24 June 2026

But this is an underestimate as many people do not recognize or report the illness. — Don Sweeney, Sacbee.com, 24 June 2026

But even short-term illness can be miserable and may require medical care, especially if dehydration becomes severe. — Julie Scott, Verywell Health, 24 June 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