Clan is a group of people who are related through a common ancestor. Some clans are matrilineal (related through the female line). Others are patrilineal (related through the male line). Although they may live far apart, members of a clan feel a close relationship to each other and usually have a strong spirit of unity. They often share property or special privileges. Most clans are exogamous. That is, the members must marry outside of the clan. Clans are often named after a totem (a symbolic animal or plant). American Indian tribes had clans such as the Bear clan or Tobacco clan.
The word clan also refers to groups of people in early Scotland and Ireland who had common ancestors and a common name, and were organized under the rule of a chief. These clans were bilateral (related through both men and women), and marriage within the clan was customary. The Scottish clans began about A.D. 1000. They carried on feuds in the Highlands, and members of a clan were expected to defend one another. Most clans lost power after the rebellion of 1745, but a spirit of clan loyalty remains among Scots. The clans are distinguished by their names—such as MacDonald and Campbell—and by their tartans, the plaids worn as emblems of clan membership (see Tartan ).