diseased

American  

[dih-zeezd] / dɪˈzizd /

adjective

1. having or affected with disease.

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diseased British  

/ dɪˈziːzd /

adjective

1. having or affected with disease

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Other Word Forms

• nondiseased adjective
• undiseased adjective

Etymology

Origin of diseased

1425–75; late Middle English disesed; compare Anglo-French diseasé. See disease, -ed ²

Explanation

When something is unhealthy or affected by illness, it's diseased. Sadly, the diseased trees in the city park may eventually need to be cut down and removed. While this adjective essentially means "sick," it's not generally used to describe people. Instead, you might use it for plants, animals, or body parts: "Hepatitis can result in a diseased liver." Diseased comes from the Old French desaise, "discomfort or sickness," from des-, "without," and aise, "ease."

Example Sentences

Research focused on using chemotherapy and radiation to wipe out diseased bone marrow, then infusing healthy donor cells to create a new immune system capable of attacking cancer and rebuilding the body’s defenses.

From The Wall Street Journal • Apr. 19, 2026

To prepare for transplant, I had two weeks of near-lethal doses of chemo to destroy my diseased bone marrow and suppress my immune system, creating space for donor cells to take hold.

From The Wall Street Journal • Apr. 19, 2026

For instance, the NHS has not invested in CT coronary angiogram machines, which allow clinicians to scan hearts to check if they are diseased.

From BBC • Mar. 24, 2026

Roberts doesn’t offer much empathy for the poor, diseased critter other than a pause when Ben momentarily ponders his reflection in a pool as Adrian Johnston’s eerie synth-piano score tinkles.

From Los Angeles Times • Jan. 9, 2026

For a long time I thought she was diseased.

From "Farewell to Manzanar" by Jeanne Houston

Related Words

• afflicted
• ailing
• infected
• infirm
• rotten
• sickly