encephalitis

American  

[en-sef-uh-lahy-tis] / ɛnˌsɛf əˈlaɪ tɪs /

noun

Pathology.

1. inflammation of the substance of the brain.

2. Also called encephalitis lethargica.  a form of this condition, caused by a filterable virus and characterized by apathy and abnormal sleepiness; sleeping sickness.

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encephalitis British  

/ ˌɛnkɛf-, ˌɛnsɛfəˈlaɪtɪs, ˌɛnsɛfəˈlɪtɪk /

noun

1. inflammation of the brain

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encephalitis Scientific  

/ ĕn-sĕf′ə-lī′tĭs /

1. Inflammation of the brain, usually caused by infection with a virus.

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encephalitis Cultural  

1. An inflammation of the brain. Encephalitis may be caused by a virus or lead poisoning, or it may be a complication of another disease, such as influenza or measles. Encephalitis can cause permanent brain damage or death. It is also possible, however, to recover from it completely.

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Other Word Forms

• encephalitic adjective
• postencephalitic adjective
• pseudoencephalitic adjective

Etymology

Origin of encephalitis

First recorded in 1835–45; encephal- + -itis

Explanation

Encephalitis is a condition that causes the brain to swell and become irritated or inflamed. Most cases of encephalitis result from a virus. The term encephalitis comes from the Greek enkephalos, "brain," and the medical suffix -itis, used for diseases characterized by inflammation. Certain kinds of infections or disorders of the immune system can result in this inflammation of the brain. Encephalitis is quite rare, and though it's often so mild that it causes no symptoms, it can be serious.

Example Sentences

There are allusions to the tragedies that befell him: the loss of a young daughter to measles encephalitis and his son’s near-fatal accident.

From The Wall Street Journal • Mar. 24, 2026

She added that Ford showed symptoms of both types of rabies - encephalitis and flaccid - which was unusual.

From BBC • Mar. 3, 2026

Certain Acanthamoeba species can cause serious illnesses, including amoebic encephalitis.

From Science Daily • Feb. 19, 2026

Complications can include bacterial infection of scabs, and much more rarely, a swelling of the brain known as encephalitis, lung inflammation known as pnemonitis, and stroke.

From BBC • Jan. 1, 2026

In some areas of the United States the mosquito vector of western equine encephalitis has developed resistance.

From "Silent Spring" by Rachel Carson