A tribe is a social group united by language and culture, and sometimes familial ties, (as a group of several clans, for example) usually a subset of a larger ethnic division. Distinctions are not always clear; some tribes are so closely related as to understand each others' dialects, other tribes in the same or related group may have very few or no similarites. Because European colonists often used the word "tribe" to describe indigenous peoples they thought of as less developed or inferior, some people today find its use offensive. In some countries the word is in common use and offence is neither implied nor taken.
The word is also sometimes used informally for a family group ("my tribe").
The word tribe was not necessarily a derogatory one, it simply conveniently classed and described groups of people. Ancient civilisations included servants and slaves in their understanding of the tribal group.
The use of the word tribe to describe groups of modern Africans is somewhat tricky. Many use the word self-referentially, others reject it, on the grounds that the English word is not applied to British tribes: Welsh, Scots and English, for example.
In U.S. law is a "tribal entity" or grouping of Native Americans recognized by the federal government. The recognition gives it certain important legal rights, especially a degree of independence from state governments. This is especially important regarding gambling laws, for it allows many tribes to operate casinos. Hundreds of other entities in the U.S. and Canada are striving for official recognition. In 2007, 562 tribes are officially recognized in the U.S.