Learn Hardcore Chinese: xiàkè yǐhòu wǒ gēn tóngxué yìqǐ huí sùshè xiūxi. - After class I go back to the dorm with my classmates to rest.

下课以后，我跟同学一起回宿舍休息。
- Time phrase 下课以后 comes first.
- This is very natural in Chinese: Time – Subject – (Other info) – Verb – Object.
- It emphasizes when the action happens.
我下课以后跟同学一起回宿舍休息。
- Subject 我 comes first, then the time phrase.
- Also correct and common.
- Slightly more focus on I as the topic.

So:

Both are grammatically fine.
Everyday speech and writing often put general time expressions like 下课以后, 明天, 晚上 before the subject, but putting them after the subject is also common:
- 明天我去北京。 / 我明天去北京。
- 下课以后我回家。 / 我下课以后回家。

Why is 跟 used here? What’s the difference between 跟 and 和 meaning with?

In this sentence, 跟 means with:

我跟同学一起回宿舍休息。
I go back to the dorm to rest with my classmates.

Both 跟 and 和 can mean with when connecting people:

我跟同学去。
我和同学去。

Differences in usage:

Spoken vs written:
- 跟 is very common in spoken Chinese and sounds slightly more casual.
- 和 is also used in speech but may sound a bit more neutral or written, depending on region.
Patterns:
- 跟 is more common in patterns like:
  - 跟……一起…… (do something together with …)
    我跟他一起吃饭。
  - 跟……说 (say to …)
    我跟老师说。
- 和 often appears in:
  - A 和 B (A and B)
    我和同学都是学生。

In this sentence, using 跟 is very natural, and most native speakers would say 跟 here. Using 和 instead would still be correct:
下课以后我和同学一起回宿舍休息。

Why do we need both 跟 and 一起? Aren’t they both kind of with / together?

You are right that they overlap in meaning, but they play different roles:

跟同学 = with classmates / together with classmates (shows the companion)
一起 = together (describes how the action is done)

In 我跟同学一起回宿舍休息:

跟同学: tells you who I am with.
一起: emphasizes we are doing the action together.

Can you drop one?

我跟同学回宿舍休息。
- Still understandable.
- Means I, along with my classmates, go back to the dorm to rest.
- The idea of together is implied but not strongly emphasized.
我和同学一起回宿舍休息。
- Keep 一起, still clear.
- Emphasizes the togetherness more.
我一起回宿舍休息。
- Odd, because 一起 needs someone to be together with, but that someone isn’t mentioned.

So the combination 跟 + person + 一起 is a very natural, common pattern:
我跟朋友一起吃饭。
他跟家人一起住。

Why doesn’t 同学 have 们? Shouldn’t it be 同学们 if it means classmates?

们 is the plural marker for people, but it is not always required, even when the meaning is plural.

同学 can mean:
- a classmate
- classmates (in general / some classmates)

In many contexts, Chinese leaves plurality to be understood from context instead of marking it:

我有同学在美国。 = I have a classmate / some classmates in the US.
下课以后我跟同学一起回宿舍休息。
Obviously we’re talking about several people going together, so 同学 is understood as plural.

When to use 同学们:

When you want to address the whole group explicitly, often as a teacher or speaker:
- 同学们，好！
- 老师跟同学们说：……

In this sentence, 同学 without 们 is more natural. 同学们 would sound like “the whole class” and often implies a teacher talking to students, which is not the case here.

Why is there no 的 like 我的同学? Why just 跟同学 and not 跟我的同学?

In Chinese, the possessive 的 is often omitted when the relationship is clear and close, especially with:

family: 我妈妈, 我哥哥 (here 的 is often dropped)
close relations or obvious roles: 同学, 同事, 朋友 often don’t need 的 if the owner is already clear.

In this sentence:

The subject is 我.
When you say 同学 in a sentence where 我 is the subject, it’s naturally understood as my classmates.

If you say 我的同学, it’s still correct, but:

It sounds a bit more specific, as if you are contrasting my classmates with someone else’s classmates.
In this neutral context, 跟同学 is simpler and more natural.

Why 回宿舍 and not 去宿舍? What is the difference?

Both 回 and 去 talk about movement, but they focus on different ideas:

去 = go (to) some place (neutral direction, just moving away from here)
回 = go back / return (go back to a place you belong to or came from)

In a school context, a 宿舍 (dorm) is understood as your living place, a place you return to, so 回宿舍 is very natural:

回宿舍 = go back to the dorm.
去宿舍 = go to the dorm (just a neutral “go”, may or may not be your own dorm).

You could say:

下课以后我去宿舍休息。
This is grammatically correct, but it doesn’t highlight the idea of going back home / back to where you stay.
下课以后我回宿舍休息。
More natural because dorm = “home base” at school, something you return to.

Why is there no 了 after 回? Would 下课以后我跟同学一起回宿舍了休息 be correct?

Putting 了 after 回宿舍 in this sentence is not natural:

下课以后我跟同学一起回宿舍休息。 ✅
下课以后我跟同学一起回宿舍了休息。 ❌ (sounds wrong/awkward)

Reasons:

Verb sequence pattern
The sentence uses a simple sequence of actions:
- 回宿舍 (go back to the dorm)
- 休息 (rest)
In many cases, Chinese just lists verbs in order without adding aspect markers:
回家吃饭 (go home and eat), 去图书馆看书 (go to the library [and] read).
When do we use 了 here?
You could add 了 at the end of the sentence to show that this already happened:
- 下课以后我跟同学一起回宿舍休息了。
  = After class, I (have) gone back to the dorm with my classmates to rest (it’s completed).
But putting 了 right after 回宿舍 and then adding 休息 is odd in this structure.

So:

No 了: neutral statement of what (typically) happens.
了 at the very end: emphasizes that this happened already.
了 after 回宿舍 but before 休息: not natural here.

What exactly does 下课 mean? Is it finish class, get out of class, or something else?

下课 means class finishes / to get out of class.

Usage:

As a verb (intransitive):
- 我们三点下课。
  Our class ends at three.
- 老师还没下课。
  The teacher hasn’t ended the class yet.
As part of a time phrase:
- 下课以后 = after class ends.
- 下课以后休息一下。 = Rest for a bit after class.

Contrast with:

上课 = have class / be in class / start class
- 我们八点上课。 We start class at eight.

So in 下课以后我跟同学一起回宿舍休息:

下课以后 = after the class is over, not during class.
The sentence describes a routine or a typical event after class.

Could I say 课下以后 instead of 下课以后?

No. 课下以后 is not a standard way to say after class.

下课以后 is the normal, idiomatic expression meaning after class finishes.
课下 sometimes appears in very specific contexts meaning outside of class time, but 课下以后 is not commonly used and would sound strange in this basic meaning.

So use:

下课以后 = after class (ends).
Not 课下以后.

Where else can 以后 go? Could I say 我以后下课跟同学一起回宿舍休息 or 下课我以后跟同学一起回宿舍休息?

以后 is quite flexible, but not every position works.

Natural positions in this sentence:

下课以后我跟同学一起回宿舍休息。 ✅
(very natural)
我下课以后跟同学一起回宿舍休息。 ✅
(also natural)
下课了以后我跟同学一起回宿舍休息。 ✅
(also fine; 了 emphasizes “after it has finished”)

Positions that are not natural or change the meaning:

我以后下课跟同学一起回宿舍休息。
This means from now on, after class I will go back to the dorm with classmates to rest.
Here 以后 = from now on / in the future, modifying the whole sentence, not just 下课.
下课我以后跟同学一起回宿舍休息。
This is awkward and unnatural; 以后 is in a strange position.

So, if you just want after class, the best forms are:

下课以后……
我下课以后……
下课了以后…… (more explicit about the completion)

Why is 一起 pronounced yìqǐ and not yīqǐ?

The word 一起 is pronounced yìqǐ (4th tone + 3rd tone), not yīqǐ.

General rule for 一 when it’s a separate word meaning “one”:

Before a 4th tone, it usually changes to 2nd tone: yí.
- 一个 → yí gè
- 一半 → yí bàn
Before 1st, 2nd, 3rd tones, it usually becomes 4th tone: yì.

However, in fixed words like 一起, the tones are fixed as part of the word:

Dictionary form: 一起 = yìqǐ.
Here 一 is not acting like the number one; it’s part of a compound meaning together.

So you should simply remember 一起 = yìqǐ.