What is a Clan? A Scottish clan (clan; from Gaelic clann, - children) consists of a group of families and individuals that often share descent and are generally defined in a common surname.
When did the Clans start? No one really knows. There were tribes in Scotland before the arrival of the Norman families and the introduction of feudalism. They generally followed the rules of tanistry in selection of the chiefs. Although the change occurred over time it is generally considered that Robert I (the Bruce), c. 1320, secured the agreement of the last chiefs to conform to feudalism. Thus granting them, in the incumbent chief, the hereditary right to ownership (rather than custodianship) of the lands, in return for allegiance to the Crown. It is this that distinguished the clans from tribes of other indigenous peoples.
What about today? The creation and management of clans is, by default, under the jurisdiction of the Court of the Lord Lyon, also known as the Lyon Court or Lyon Office. This is a standing court of law that regulates all aspects of heraldry in Scotland. They regulate the rightful heir to the undifferenced arms of the clan. The clan is considered to be the chief's heritable estate and the chief's Seal of Arms is the seal of the clan as a "noble corporation." Under Scots law the chief is recognised as the head of the clan and serves as the lawful representative of the clan community.
Clans are Highland and families are Lowland? No, this is not the case. The terms are used interchangeably in Scottish law. It is correct to say the MacDonald family as it is to say Clan Pringle.
What about Septs? Septs are no longer recognised and not needed on wikitree. While once used to show families affiliated with a particular Clan, they were time dependent. There was never any official list. On wikitree, as a general rule, it is more appropriate to associate a profile with the family name.
Who can become a member of a clan? This has varied over time. Historically a family, or group of families, banded together, bounded by geography, for protection and would form a clan. The chief was chief of his clan territory and all the persons who lived there, although members of his immediate family, might owe him allegiance wherever they were living. This was a clan. A chief was also entitled to add to his clan, often through territorial gains or by the adoption of families or groups of families. It is the chief of a clan that can decide who are members of their clan. Today, without the same geographical constraints, membership is more relaxed. The generally applied rule is "Every person who has the same surname as the chief is deemed to be a member of the clan. Equally if a person offers his allegiance to a particular Clan by joining a clan society (recognised by the office of the Lord Lyon by the granting of Armorial Bearings) he can be deemed to have elected to join that particular clan and should be viewed as a member of that clan unless the chief particularly states that he or his name group are not to be allowed to join the clan."
All members of the clan are descendants of the first chief. No, this is not the case. It would be inappropriate, particularly on wikitree, to assume that a person was a descendent of a chief. Care needs to be taken with ancestors, particularly around the period of the 17th and 18th Century where soldiers captured often gave the name of their clan as their last name even if they knew their "correct" surname.
Do women always take the name of the husband's clan? No, there are plenty of cases in history where the man takes on the woman's family name and clan. Membership is a choice, in general practise today a woman can be of a different clan to her husband.
It is impossible to be a member of two clans. While this is a general rule there are exceptions. Exceptions may arise due to time differences or marriage. They may also arise due to families, with the same name, arising from different source families. An example is Henderson; the current clan chief is Alistair Henderson of Fordell, the historical seat of the clan is in Fife. However families of that name (in Gaelic is Maceanruig) were part of the MacDonald of Glencoe and were also associated with Clan Gunn, in north Scotland. There is no known family association between them however they are all, today, regarded as part of Clan Henderson. It would be correct, on wikitree, to also associate the piper at Glencoe as a member of Clan MacDonald as this was historically correct.
The Lyon Court maintains a List of all Clans, which can be found on Electric Scotland as the Official Scottish Clans and Families and wikipedia. There are other sources with varying degrees of accuracy depending on when the page was developed. Amongst these clans are those that have a legally recognised Chief and those, armigerous, that do not. Wikitree, due to its historical nature, maintains entries for any recognized Clan. To facilitate management of the project we maintain "Teams" to manage these clans. They can be found on the clan pages.