I understand the word "idempotent" to describe an action where the second time that action is applied, it has no additional effect. In other words, redundant operations have no effect.
The first usage of the word seems to have been made in a mathematical context, but it is also widespread in computer science (see usage here). As a computer science student this terminology is very useful, but it can also feel odd saying the word. There are even stackexchange questions asking how to pronounce it!
I'd like to be able to express the meaning of the word idempotent in a casual setting using only one word without sounding too technical (a two-word solution may also be interesting).
I tried to find synonyms in a dictionary but found none. I tried to translate to other languages to see if I could adopt a new word, but I couldn't find one.
As a last resort, I don't mind if I have to create my own word or phrase. I was thinking of saying something has "null redundancy". Maybe I could shorten it to be "nullred", but that sounds silly.
Sample Sentence
A credit card transaction should be < word > so that you don't get charged twice.
Another example
Instead of saying "It doesn't do anything the second time", shorten to "It isn't < word >"
I don't care whether the word is a noun, verb, or adjective as long as it makes sense. I think it is best suited as a noun and adjective though.
TL;DR
Do any synonyms of the word idempotent actually exist?
Using latin roots or some other method, can you make a substitute word that you think makes sense?