Having a set I need to take an arbitrary element which is not in this set.
I know that existence of such elements for every set can be proved in ZF.
My question: Are there any established notation/terminology for such elements?
Having a set I need to take an arbitrary element which is not in this set.
I know that existence of such elements for every set can be proved in ZF.
My question: Are there any established notation/terminology for such elements?