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

For example, dementia, addiction, severe depression, personality changes following illness, emotionally unavailable partners. —Maia Niguel Hoskin, Forbes.com, 27 May 2026

His request for mental health treatment had been put off, records show, and staff had forbidden Rayo from making his nightly call to his mother as a precaution intended to prevent the spread of illness. —CBS News, 27 May 2026

Busch continued to race — and win — while dealing with an illness in the weeks leading up to his death. —Alex Andrejev, New York Times, 27 May 2026

Salmonella can cause serious and sometimes fatal illness in young children, elderly people or people with weakened immune systems. —Los Angeles Times, 27 May 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