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

After her diagnosis, her doctor taught her about the illness and what to expect during treatment. — Durrie Bouscaren, NPR, 25 July 2026

In the initial stages of infection, the pathogen would resemble a known illness—one vulnerable to standard vaccines or drug remedies. — Gideon Lewis-Kraus, New Yorker, 25 July 2026

Lab testing a stool sample to confirm the illness also takes time. — Brenda Goodman, CNN Money, 25 July 2026

His father became his training partner, and then Hernandez lost him in 2019 to illness. — Joe Davidson, Sacbee.com, 25 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