TOEFL listening question : phrase : "sitting in on a course"

Question

A TOEFL listening section textbook gives me a phrase such as below

Professor

Another option for you this term would be to audit a course or two -- you wouldn't have to pay regular fees and full tuition for it.

Student

Interesting. I never thought about sitting in on a course.Also, I suppose that if after a week or two, I really thought I should enroll in the course, I could always add it, or for that matter, if a course doesn't work out, I could drop it

After googling the word at the title, a page describing this situation appeared.

Saying,

Usually, in the Eastern USA, in the universities that I know, "sitting in on" means being in a class that one is not taking for a grade. The regular students take the class, they sit in it. A visitor (a student not enrolled in the class, or a visitor - a friend or relative of one of the students taking the class) may sit in on it, and listen to the lecture. I'm not sure if regularly attending the class without taking it - like for example a teaching assistant attending the class to see what exactly the professor is teaching - qualifies as "sitting in on" it.

In addition to it, What is aggravating me about this sentence is, I can't catch the relationship between the phrase at the title and the professor's word "audit" and the student consequent "past" sentence.

However though, is the description of the page I looked up at still correct?

Answer 1

"To sit in on" has a number of similar meanings. It generally implies one's presence at an presentation, meeting or teaching event where one is not the primary intended audience.

For example: "Michael sat in on the meeting with Staples'n'Gophers Co." would imply that Michael attended the meeting but was not one of the main participants. He may have been there as part of his training or education, to bring him up to speed with the subject matter of the meeting or to otherwise benefit from observing and listening to the meeting.

The definition of "sitting in on" you have is more specific to academic courses and refers to the process of attending a course without formally enrolling. In your textbook this is being presented as a synonym for "auditing" the course. Note that this use of "audit" is a US English definition and does not necessarily mean the same thing in other countries. "Sitting in on", however, does appear to be a more universal phrase.

Answer 2

The verb is sit in + [ on {something} ]

If you don't want to take the course officially, you can sit in on it.

If you are an eavesdropper or a spy, you can listen in on a conversation.

If you are an interloper, you can muscle in on a situation.

If you did not notice the necktie on the doorknob, you could barge in on your roommate and his girlfriend.