Tuath is an old Irish word. It means 'people', 'tribe' or 'nation'. It referred to the people who lived in a shared territory. It also referred to the territory they controlled. Each tuath had a clan chief who acted as leader and representative of the people who lived there. The average size of a tuath was about 15-25 km across, with a population of several thousand. There are many parallels between modern parish boundaries and those of the ancient tuaths.