“Tribe” really only applies in pre-state societies. In general, members of a given “tribe” all trace descent from the same legendary ancestor, who were usually related to the other tribal ancestors of the same “nation” (“gentes”). Thus, one would have the Germanic “nation” or “people” that would be divided into the “tribes” of the Franks, Alans, Ostrogoths, Visigoths, etc.
In the Americas, “nation” was replaced by “language group” in scholarly discourse. Thus, one has the “Iroquoian Language Group” which would be divided into the Cayuga, Onandaga, Seneca, Huron, etc.
Then, each “tribe” would divide further along ancestral lines, but the methods of division vary greatly. In North America, “band” is a term that is used from time to time.
To confuse matters greatly, North American groups that the Romans probably would have called “tribes” now call themselves “nations”, although they far more closely resemble the classical concept of “tribe” than they do “nation”.
It should be noted that “Iroquoian Language Group” is not the same as “The Iroquois”, which refers to the Six Nations Federation of tribes.
“Sept” is of fairly limited use. It is a variant of the word “sect” (as in “section”). In Irish use, a “sept” is a larger group than is a “clann”–clanns are in septs. In Scottish Gaelic use, it’s reversed.
In either case, “sept” came from Latin, so it’s not an original Celtic term.
Huh, interesting. When I first came across the word “sept” it was when I learned that the Menzies clan was divided into 7 “septs”. I always thought it had some connection to the number 7.
Sept has no connection to seven at all. Other Scottish clans have different numbers of septs. There are more than seven Irish septs, and the septs all have different numbers of clanns within them.