If you need to define a word in your paper, the definition usually comes from a glossary in the back of a book. To properly attribute this definition you will need to cite it according to the American Psychological Association (APA) style guidelines.
Encephalitis is inflammation of the brain tissue. It's most often caused by viral infections. In some cases, bacterial infections can also cause encephalitis.
1 Encephalitis is a brain inflammation that causes sudden fever, vomiting, headache, light sensitivity, stiff neck and back, drowsiness, and irritability.  Epilepsy is a brain disorder in which the person has seizures. There are two kinds of seizures, focal and generalized. There are many causes of epilepsy.