An epigraph is a phrase, quotation, or poem that is set at the beginning of a document or component. It is often used to introduce an idea that will be explored in the text. A MOTTO is a phrase that expresses a rule of conduct or a guiding principle, while an INSCRIPTION is a phrase or words written or engraved on a surface. In this context, an epigraph could be a MOTTO or an INSCRIPTION that is used to introduce a document or component.