What is the difference between a teaching assistant and an instructor? It seems to me that the terms "Teaching Assistant" and "Instructor" refer to a variety of positions. At some places, a teaching assistant is responsible for things like helping the actual lecturer by handing out papers, grading homework, etc., and instructors hold recitation sessions.

At other places, I saw the term "instructor" referring to the lecturer giving the course, while a teaching assistant is the person doing anything else (recitations, grading etc.).

Is there some widely accepted definition of the two positions?

For context: The question arose because I wasn't sure whether I'm using the correct terms in my CV -- I am a math graduate student, and I would like to make a distinction between jobs in which I only graded course assignments/final exams, and courses in which I held recitation classes* (and also participated in grading the final exams). Is it OK to use "Instructor" for the latter? What should the former be referred to as?

*In the course I'm currently teaching, the recitations are planned and written by the ones giving them (without the professors' supervision). Also, the people giving the recitations are not necessarily grad students (some already hold a PhD). I'm elaborating on that because from what I've seen, some of it could be relevant for the definition of the job.
No, there really is no universal definition of the terms; I have been a "teaching assistant" and an "instructor" at the same school for basically the same position.

The only thing that I would say is that the term "teaching assistant" tends to imply a position that does not have significant lecturing responsibilities, although she may be responsible for nearly everything else in the course (creating and grading homework and exam problems, interacting with students, conducting recitations sections, and so on). Note that this does not mean that the TA might not carry out a "spot lecture" or two; but this is not an expectation of the position overall. 

In general, I would avoid this problem by doing two things:


Listing on my CV the "job title" that the school assigns to the role you carried out.
Provide a short list of the duties your position entailed.


In this way, there is no ambiguity or misconception that can result, since you're providing all the information needed to understand the breadth of your teaching experience.