Sui generis
In local government, a "sui generis" entity is one that does not fit with the general scheme of local governance of a country. For example in England, the City of London and the Isles of Scilly are the two "sui generis" localities, as their forms of local government are both (for historical or geographical reasons) very different from those of elsewhere in the country. 
In a press conference during which reporters were trying to analyse his political personality, Huey Long said, "...say that I am "sui generus", and let it go at that."
Secundogeniture
A secundogeniture (from "following, second," and "born") was a dependent territory given to a younger son of a princely house and his descendants, creating a cadet branch. This was a special form of inheritance in which the second and younger son received more possessions and prestige than the apanage which was usual in principalities practising primogeniture. It avoided the generational division of the estate to the extent that occurred under gavelkind, and at the same time gave younger branches a stake in the stability of the house.
The creation of a secundogeniture was often regulated by a house law. The younger sons would receive some territory, but much less than the older brother, and they would not be sovereign. Examples of such house laws would be