Ostracon

An ostracon (Greek: ὄστρακον ostrakon, plural ὄστρακα ostraka) is a piece of pottery (or stone), usually broken off from a vase or other earthenware vessel. In archaeology, ostraca may contain scratched-in words or other forms of writing which may give clues as to the time when the piece was in use. The word is derived from Greek ostrakon, meaning a shell or a shard of pottery used as a voting ballot. It is a common error for the plural form ostraca to be used as the singular for ostracon.