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

Humans were historically safer in groups, so the brain interprets isolation as a stressor, releasing cortisol that can lead to inflammation and illness, explains neuroscientist Ben Rein, author of Why Brains Need Friends. —Holly Haber, Dallas Morning News, 20 Mar. 2026

The four-person crew has entered quarantine to avoid illness ahead of the historic lunar mission. —Eric Lagatta, USA Today, 20 Mar. 2026

The positive pregnancy test came almost at the same time as the actor’s mother was diagnosed with an aggressive terminal illness. —Rafa Sales Ross, Variety, 20 Mar. 2026

The ability to self-schedule helps Young manage her autism and a chronic illness called postural orthostatic tachycardia syndrome, which can cause a rapid heart rate or dizziness when standing up. —ABC News, 19 Mar. 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