Taxonomy term individual occupant can anyone tell me if there is a way to set the terms under a taxonomy to have only one node?

I am building a system which is based on taxonomies but each term should contain only one one. If any user tries to save a node under an occupied term, I need it to be disallowed.

Can anyone help with some insight?
you could use a hook_form_alter when a node is saved and check if the selected term has already been used. Then just show an error message.