Plethron (Greek: πλέθρον, plural plethra) is an ancient unit of Greek measurement equal to 97 to 100 Greek feet (ποῦς, pous; c. 30 meters), although the measures for plethra may have varied from polis to polis. This was roughly the width of a typical ancient Greek athletic running-track. The plethron continued to be used in the Byzantine Empire, where its variant uses were ultimately codified to refer to an area defined by sides of 100 feet or 40 paces (βῆμα, bema). Ultimately, the unit came to be known as the "stremma", which continues as a metric unit in modern Greece.