Sui generis
In sociology, the "sui generis" is what has been externalized, then internalized in the overall public and becomes a part of society that simply exists in its construct. It is not something that is not thought to have been created, because it is imbedded in everyone's way of thinking and being. Instances include the idea of love, or going to school, or clothing belonging to a specific gender. These examples are "sui generis" for they simply exist in society and are widely accepted without thoughts of where they come from or how they were created.
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