Hello, I've studied that Нести-носи́ть means to bring. The first is the concrete form, the latter is the abstract one. If you add some prefixes like, for instance, при, you form a perfective verb with the concrete form (принести) and an imperfective one with the abstract form (приноси́ть). Thus far is easy theoretically. What my grammar book doesn't explain is which one is the concrete form and which one is the abstract form. So, in brief, принести is the concrete or the abstract form? And приноси́ть? Thank you, I'll use this answer with all the other verb.