What does encephalitis mean?
Encephalitis is a serious medical condition defined as inflammation of the brain itself, most commonly triggered by a viral infection — herpes simplex virus is a frequent cause — though it may also arise from bacterial infection, parasites, or an autoimmune response in which the body's own immune system attacks healthy brain tissue. Typical symptoms include fever, severe headache, vomiting, confusion, drowsiness, and sometimes seizures or paralysis, making it a potentially life-threatening emergency that requires prompt hospital care. The word functions as a formal medical noun, appearing almost entirely in clinical, journalistic, and public-health contexts, and its plural form 'encephalitides' is used when distinguishing specific varieties such as Japanese encephalitis or tick-borne encephalitis. Because the brain is enclosed within the skull, swelling from inflammation can be especially dangerous. Understanding this term matters both for reading health news intelligently and for appreciating how Greek roots still structure modern medical vocabulary.
nounInflammation of the brain, typically caused by a viral infection or an autoimmune reaction, and often accompanied by fever, headache, confusion, or neurological impairment.
- Inflammation of the brain tissue, most often caused by viral infection.
"The patient was hospitalized after mosquito-borne encephalitis swept through the region."
"Doctors diagnosed viral encephalitis after the fever was followed by seizures and disorientation."
"Public health officials launched a vaccination campaign against Japanese encephalitis across Southeast Asia."
Rarely used outside specialist medical contexts; in ordinary usage 'encephalitis' functions as an uncountable noun.
"The textbook surveys several viral encephalitides found in temperate climates."
Its plural is 'encephalitides' — and the word literally means 'inflammation inside the head' in ancient Greek.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Words that share this root
How encephalitis is actually used
A formal medical term used chiefly in clinical and scientific writing rather than everyday conversation; it is uncountable in general use but takes the learned plural 'encephalitides' when referring to distinct types.
Easily confused with encephalitis
Meningitis is inflammation of the membranes surrounding the brain and spinal cord, whereas encephalitis is inflammation of the brain tissue itself, though the two can occur together as meningoencephalitis.