In Durkheim's concepts, what does sui generis mean?

The Latin phrase "sui generis" means something like
"unique" or "of its own kind."  Durkheim uses the phrase to describe social facts about
societies.  He argues that social facts about a society are sui generis.  He says that
they are created by the society and are unique to that
society.

Durkheim is arguing that social facts are not
things that we can control.  Rather, they have been built up by the cumulative
experience of all that has come before us.  Because of this, they are sui generis.  They
are unique and they are not things that we can change.

So,
to Durkheim, the phrase "sui generis" refers to things that are outside our control.  He
uses the phrase to refer to social facts about our society that act upon us but which we
cannot ourselves change.