Conjunctivitis, commonly known as pink eye, is an inflammation or infection of the conjunctiva, the thin, transparent membrane that covers the white part of the eye and the inner surface of the eyelids. This condition is characterized by redness, itching, and a gritty feeling in the eye, and it can affect one or both eyes. While conjunctivitis is usually not serious and often resolves on its own, it can be uncomfortable and, in some cases, contagious.