Codomain and range are not the same - range is the set of numbers that actually come out, codomain is like, some kind of set that those numbers are drawn from l

Codomain and range are not the same - range is the set of numbers that actually come out, codomain is like, some kind of set that those numbers are drawn from like the integers (I'm not even sure, but it has never mattered enough for me to find out). For the case of a bijection of course the codomain and range are going to be the same, but not in general. But, there are ocassional renamings of things that usually improve the overall lingo. Some things I learned one way but they have now been renamed. E.g. I learned about 'one-to-one and onto' functions instead of 'bijective' functions. I think you'll agree 'bijective' is better than 'one-to-one and onto'. The same happens in programming languages and libraries when they rename functions from time-to-time. For a while there are inconsistencies whilst both are in use, sometimes permenently if the new name comes about by a creation of a new programming language or dialects. It's true that searching for a strange symbol you don't know the name of (or even have the unicode character - if it exists - on hand) is hard. If you knew they were called "blackboard-bold Z" you'd be able to find out via google what it meant pretty easily. (I am totally assuming you mean blackboard bold by writing ZZ and NN, otherwise I also don't know what those mean)