Hepatitis (plural hepatities) implies injury to liver characterized by presence of inflammatory cells in the liver tissue. Etymologically from ancient Greek hepar (ηπαρ) or hepato- (ηπατο-), meaning 'liver,' and suffix -itis, denoting 'inflammation' (c. 1727). The condition can be self limiting, healing on its own, or can progress to scarring of the liver. Hepatitis is acute when it lasts less than 6 months and chronic when it persists longer. A group of viruses known as the hepatitis viruses cause most cases of liver damage worldwide. Hepatitis can also be due to toxins (notably alcohol), other infections or from autoimmune process. It may run a subclinical course when the affected person may not feel ill. The patient becomes unwell and symptomatic when the disease impairs liver functions that include, among other things, screening of harmful substances, regulation of blood composition, and production of bile to help digestion.