An ostracon is a piece of pottery, usually broken off from a vase or other earthenware vessel. In an archaeological or epigraphical context, ostraca refer to sherds or even small pieces of stone that have writing scratched into them. Usually these are considered to have been broken off before the writing was added; ancient people used the cheap, plentiful, and durable broken pieces of pottery around them as a convenient medium to write on for a wide variety of purposes, mostly very short inscriptions, but in some cases very long.

Epigraphy is the study of inscriptions, or epigraphs, as writing; it is the science of identifying graphemes, clarifying their meanings, classifying their uses according to dates and cultural contexts, and drawing conclusions about the writing and the writers. Specifically excluded from epigraphy are the historical significance of an epigraph as a document and the artistic value of a literary composition. A person using the methods of epigraphy is called an epigrapher or epigraphist. For example, the Behistun inscription is an official document of the Achaemenid Empire engraved on native rock at a location in Iran. Epigraphists are responsible for reconstructing, translating, and dating the trilingual inscription and finding any relevant circumstances. It is the work of historians, however, to determine and interpret the events recorded by the inscription as document. Often, epigraphy and history are competences practised by the same person. Epigraphy is a primary tool of archaeology when dealing with literate cultures. The US Library of Congress classifies epigraphy as one of the auxiliary sciences of history. Epigraphy also helps identify a forgery: epigraphic evidence formed part of the discussion concerning the James Ossuary.