Tribe

A tribe was a type of social group, usually smaller than a nation. They were common in civilisations that were not technologically advanced.
The Doctor encountered many human tribes throughout time and space, from the Tribe of Gum on prehistoric Earth (TV: An Unearthly Child) to the Sevateem‎ and the Tesh‎ in the far future. (TV: The Face of Evil) The Tribe of the Free lived on Ravolox in 2000000. (TV: The Mysterious Planet)
In the 5th century, the Roman Empire suffered attacks from many tribes, including the Goths, Ostrogoths, Visigoths, Gepids, Alans, Franks, Burgundians, and Huns. (PROSE: Combat Magicks)
In Africa, the Fourth Doctor, Sarah Jane Smith and Harry Sullivan encountered a tribe in Nyasaland. (PROSE: To Kill a Nandi Bear)
The Efik were a tribe in the Kingdom of Dahomey. (PROSE: White Darkness)
In South America in 1924, George Cranleigh encountered the Kojabe tribe and another tribe led by Latoni. (TV: Black Orchid) The Second Doctor, John and Gillian encountered a South American tribe and helped them fight off an enemy tribe. (COMIC: The TARDIS Worshippers)
Other species which formed tribes included Lakhotha, (PROSE: Scribbles in Chalk) Neanderthals, (TV: Ghost Light) Silurians, (TV: The Hungry Earth / Cold Blood) Swampies, (TV: The Power of Kroll) and the Sycorax. (TV: The Christmas Invasion) The First Doctor, John and Gillian encountered a hostile tribe on an Earth-like planet. (COMIC: The Didus Expedition)