When one is dating consistently with one guy, how would one know if they are in a relationship? Would it be rude or inconsiderate to ask?

well, are you dating or… are you going on dates? Those aren’t the same thing. If you’ve talked it out and both say that you are indeed dating then, yes, you are in a relationship. If he hasn’t said something and you are feeling uncomfortable with the ambiguity then you need to ask him point blank to clarify things. It’s not fair to either of you to have unspoken expectations. I’m a firm believer in open, honest communication with all friends/lovers/boyfrans. If they can’t handle you asking a question like that of them, then they’re no good to be pursuing for a relationship.