"register in" or "register at"

Question

What preposition I should use after the verb "register" in this context:

Students registered in/at the course.

Answer 1

Between the two, in makes much more sense than at.

At would only be used when discussing where you were when you registered:

I registered for the course at the lecture hall.

But both in and for can be used immediately after registered, depending on if you are talking about the actual act of registration or the fact that a name is found in a list (a book or database).

On the first day of school, I registered for a course.

Here, you are talking about the actual act of signing up for something.

But:

On the first day of school, I registered myself in a course.

This implies that you are talking about having got your name entered into a course registration list.

The prepositions can normally be interchanged without the meaning being lost. (Although note that, for instance, the construction registered myself for a course sounds awkward.)

Other contexts also makes a difference.

Consider:

Are you still registered in the course?
Are you still registered for the course?

In this case, the former sounds more natural because you're talking about if your name is still found in a list of registered students.

Meanwhile, the second sentence sounds strange because you think it should be rephrased as Are you still registering for the course? But that has a different meaning, and isn't what's intended if the registration process has been over for a while.

Answer 2

You register FOR a course.

But if you mean where or how you do the registering, you might do it AT the university or ON a web site.