"in the next" is correct sometimes?

Question

Today I thought of the possibility of an existence of a correct sentence that has the following words "in the next", because it seems to me now not logic to have such sentence since it has a needless preposition. For example:

He'll be at the university in the next semester.

It seems the preposition "in" is really needless here. But my question if it's considered ungrammatical and not natural, or both are considered grammatical?

N.b. It somehow sounds to me like "in the afternoon" that already has one preposition (after). I mean to my non native English ears it sounds much more natural to say "I'll be there afternoon." than to say "I'll be there in the afternoon.".

Answer 1

In the next is unusual in this context.

We use the phrase in both time references in the next few minutes/months and spatial references: in the next room.

But we don't use it when talking about when we will be somewhere or be going somewhere (unless we mean during or in the course of).

We omit both in and the:

He'll be seeing her next week

He'll be attending classes this afternoon

He'll be studying history next term

and, coming to your phrase

He'll be at university next semester

However, we can talk about in the next semester when mean in the course of or during.

He'll make up his mind about his career options in the next semester

but not in the sense in which you use the phrase.

Regarding your afternoon example, we would say:

I'll be there this afternoon (or tomorrow afternoon)

although in the is again used to mean during the

I'll finish the job in the afternoon

Answer 2

I do not disagree with R. Sole in what he says in his answer, but he does not mention what is a dangerous misconception in your question.

"Afternoon" is one word, specifically a noun. The phrase "in the afternoon" is quite common and perfectly grammatical.

"He goes to French class in the afternoon" is grammatical and idiomatic. "He goes to French class in afternoon" is not.

What must be a nightmare for a non-native speaker is that "afternoon," a single word, and "after noon," a prepositional phrase, may both be used to convey the same meaning, but have different syntactical forms.

"I shall arrive in the afternoon" and "I shall arrive after noon" have the same meaning, but different forms. No wonder you have questions.