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

• 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

Those over 60 or with certain medical conditions are at a greater risk for severe illness. —Caroline Neal, Louisville Courier Journal, 2 Oct. 2025

Mice contaminate food, chew up everything in sight, and spread illnesses through their urine, saliva, and droppings, says Sheldon Owen, a wildlife extension specialist at West Virginia University. —Arricca Elin Sansone, Southern Living, 1 Oct. 2025

The nonprofit promotes mental health and illness prevention through education, research and advocacy. —Kristen Rogers, CNN Money, 1 Oct. 2025

Duran, like many of the Phillies over the final 10 days, was fighting an illness. —Matt Gelb, New York Times, 1 Oct. 2025

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