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.
Issue (genealogy)
"Issue" typically means a person's lineal descendants—all genetic descendants of a person, regardless of degree. Issue is a narrower category than heirs, which includes spouses, ancestors, and collaterals (siblings, cousins, aunts, and uncles). This meaning of issue arises most often in wills and trusts. A person who has no living lineal descendants is said to have died without issue.