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

The family never found out about the nature of illness. —Susana Erazo, CNN Money, 7 Feb. 2026

Artemis astronauts leave quarantine Delaying the mission until March means the astronauts have exited quarantine at the Johnson Space Center in Houston, which is protocol ahead of spaceflights to ensure crews avoid exposure to illnesses. —Eric Lagatta, USA Today, 6 Feb. 2026

One of the illnesses that can be especially serious for young children is respiratory syncytial virus (RSV). —Michael Cromer, The Orlando Sentinel, 6 Feb. 2026

Free radicals are molecules that damage cells, which can lead to illness and negatively impact body function. —Bestreviews, Chicago Tribune, 6 Feb. 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