For example, in functional languages, variables are single assignment and their values are immutable once assigned. So they have two states unbound and bound, once bound they can't be changed.
Is there some mathematical term or other computer science term that is most appropriate for such as thing? Something that semantically doesn't imply variance or mutability.
If not there doesn't exist such as term and if you were designing a language that had such constructs, what other than the word variable would you use to for these?
I am not really looking to poll for ideas, I am trying to figure out if there is already an accepted industry ( any industry ) term for such a thing.