Learn Hardcore Chinese: jiàoshì lǐ de lājītǒng mǎn le, tā shùnbiàn bǎ lājī ná dào lóuxià. - The trash can in the classroom was full, so he took the trash downstairs on the way.

In Chinese, many adjectives also act as stative verbs. 满 here is a verb meaning “to be full,” so 垃圾桶满了 literally means “the trash can has become full / is full now.”

You normally don’t use 是 before this kind of predicate:

✔ 垃圾桶满了。= “The trash can is (now) full.”
✘ 垃圾桶是满了。

是 + adjective is used in specific contrasts or emphatic structures (like “it is full, but…”), not for a simple description.

What exactly does 了 mean in 满了? Is it past tense?

Here 了 marks a change of state, not simple past tense.

满 = (to be) full
满了 = “(has) become full,” “is now full (but wasn’t before).”

So 了 is telling you that the situation has reached a new state: the trash can wasn’t full before, and now it is. It often implies the event already happened, so it often refers to the past, but its core function here is change-of-state, not “past tense” in the English sense.

How does 的 work in 教室里的垃圾桶?

教室里的垃圾桶 literally breaks down like this:

教室里 = inside the classroom
的 = linker, turning the phrase before it into an attributive modifier
垃圾桶 = trash can

So 教室里的垃圾桶 = “the trash can that is in the classroom” / “the classroom’s trash can (the one located inside).”

Structure:
> [Location phrase] + 的 + [noun]
> 教室里 + 的 + 垃圾桶 → the trash can that is in the classroom.

Why do we say 教室里的垃圾桶, not just 教室的垃圾桶?

Both exist, but the nuance differs:

教室里的垃圾桶 – focuses on location: the trash can in the classroom (physically inside).
教室的垃圾桶 – more neutral “the classroom’s trash can,” could be interpreted as belonging to or associated with the classroom, without emphasizing “inside.”

In everyday speech, if you physically picture the bin in the room, 教室里的垃圾桶 is more natural because of 里 (“inside”).

Is 里 (“inside”) always needed after a place word like 教室?

No, it depends on what you want to say.

教室 = the classroom (as an entity / area)
教室里 = inside the classroom

In 教室里的垃圾桶, you want to specify inside that space, so 里 is used.

Examples:

我在教室。= I’m at the classroom (general location).
我在教室里。= I’m inside the classroom (emphasis on “inside”).

In many cases, both can be used, but 里 adds the sense of interior.

What does 顺便 mean here, and where can it go in the sentence?

顺便 means “by the way,” “while (you’re) at it,” “incidentally,” usually describing doing something conveniently at the same time as another main action.

In:
> 他顺便把垃圾拿到楼下。

it means “He took the trash downstairs incidentally / while he was at it.”

Common positions:

Subject + 顺便
- Verb phrase
  - 他顺便买了点水果。= He bought some fruit on the way / while he was at it.

You could also say:

他顺便把垃圾拿到楼下。✔ (most natural)
他把垃圾顺便拿到楼下。△ possible, but less natural; 顺便 usually goes before the whole action, not in the middle.

What is the function of 把 in 他顺便把垃圾拿到楼下?

把 introduces a “disposal” construction, highlighting what happens to an object.

Pattern:
> Subject + 把 + Object + Verb (+ complement)

他顺便把垃圾拿到楼下 focuses on what is done to “the trash” — it is carried downstairs.

Nuance:

他顺便拿垃圾到楼下。= He incidentally took trash downstairs. (more neutral)
他顺便把垃圾拿到楼下。= He incidentally handled/dealt with the trash by taking it downstairs.

The 把 sentence often feels more like “take care of / deal with X in this particular way.”

Can we leave out 把 and just say 他顺便拿垃圾到楼下? What’s the difference?

Yes, you can say:

他顺便拿垃圾到楼下。✔

This is grammatical and understandable. The differences:

With 把 (把垃圾拿到楼下) – emphasizes garbage as the affected object: “He (incidentally) took care of the trash by carrying it downstairs.”
Without 把 (拿垃圾到楼下) – more neutral description of the action “take trash downstairs,” slightly less focus on the resulting handling of the trash.

In everyday speech, both are fine; 把 is very common when you want to clearly present “object + result.”

How does 拿到 work here? What’s the difference between 拿到楼下 and 拿去楼下?

拿到 = 拿 (to take, hold, carry) + 到 (direction/result complement: “to / reach”).

拿到楼下 = “carry (it) to downstairs / to the downstairs area.”
It implies reaching that destination.

Compare 拿到 vs 拿去:

拿到楼下 – neutral, result-focused: end up at downstairs.
拿去楼下 – more emphasis on taking something away to there, often from the speaker’s current location. It can sound a bit more like “take it (away) down there.”

In many contexts, both could be used, but 拿到楼下 is the more standard phrasing here.

What exactly does 楼下 mean? Is it “first floor,” “downstairs,” or “outside”?

楼下 literally means “below the floor (you’re on)” → downstairs / the lower floor. Context decides the precise place:

在楼下 = downstairs (in the area downstairs)
去楼下 = go downstairs
拿到楼下 = take (something) downstairs

It doesn’t inherently mean “outside,” but in many real-life situations, the trash area might be outside the building downstairs, so in practice it can imply going outside, even though the literal meaning is just “downstairs.”

Why doesn’t 垃圾桶 have a measure word like 一个垃圾桶?

Chinese only requires a measure word when you have something like:

a number: 一个垃圾桶 (one trash can)
a demonstrative: 这个垃圾桶 (this trash can)
certain quantifiers.

Here, 垃圾桶 is just a bare noun used as a definite, known thing from context: “the trash can.” No numeral or demonstrative appears, so no measure word is needed:

教室里的垃圾桶满了。= “The trash can in the classroom is full.”

If you needed to specify “one trash can in the classroom,” you’d say:

教室里有一个垃圾桶。= There is one trash can in the classroom.

Why is 垃圾 (“trash”) used without a measure word in 把垃圾拿到楼下?

Mass or uncountable nouns often appear without a measure word when you talk about them in general:

垃圾 – trash, garbage (mass noun)

So:

把垃圾拿到楼下。= “take the trash downstairs”

If you want to talk about a specific amount, you add a measure word:

一袋垃圾 = a bag of trash
一桶垃圾 = a bin-full of trash
一些垃圾 = some trash

But for general “the trash,” 垃圾 alone is natural and normal.

Could the subject 他 be omitted in the second clause? For example: 教室里的垃圾桶满了，顺便把垃圾拿到楼下。

In this kind of written, standalone sentence, you normally keep the subject 他 in the second clause:

教室里的垃圾桶满了，他顺便把垃圾拿到楼下。✔

If the subject stays the same, Chinese can sometimes drop it in follow-up clauses, especially in casual speech or when the context is extremely clear. But:

教室里的垃圾桶满了，顺便把垃圾拿到楼下。

without 他 sounds a bit like a command (“Since the trash can is full, (you) should by the way take the trash downstairs”), or just incomplete in isolation.

So for a neutral narrative sentence, keep 他:
> …，他顺便把垃圾拿到楼下。