Chúng tôi phải đợi vì nhiều người đang xếp hàng.

Chúng tôi means we/us, but specifically excluding the listener.

So:

• chúng tôi = we (not including you)
• chúng ta = we (including you)

That distinction is something English usually does not mark.

In this sentence, Chúng tôi phải đợi... suggests we had/have to wait, and the speaker is probably not including the person they are talking to.

Phải means must, have to, or need to.

In Chúng tôi phải đợi, it gives the idea of obligation or necessity:

• phải đợi = have to wait

It often works like a modal in English:

• Tôi phải đi. = I have to go.
• Bạn phải học. = You must study.

So the structure is:

• subject + phải + verb

Here:

• Chúng tôi = we
• phải = have to / must
• đợi = wait

Yes, in many everyday situations, đợi and chờ both mean to wait.

For example:

• Tôi đợi bạn.
• Tôi chờ bạn.

Both can mean I’m waiting for you.

There can be slight differences in style or regional preference, but for a learner, it is usually safe to understand them as near-synonyms. In this sentence, phải đợi simply means have to wait.

Vietnamese verbs do not always match English prepositions.

In English:

• wait for someone

In Vietnamese:

• đợi ai
• chờ ai

So Vietnamese usually does not need a separate word for for here.

Examples:

• Tôi đợi bạn. = I’m waiting for you.
• Anh ấy chờ xe buýt. = He is waiting for the bus.

That is very common: Vietnamese often expresses the idea directly with the verb, without an extra preposition like English uses.

Vì means because.

In this sentence:

• Chúng tôi phải đợi vì nhiều người đang xếp hàng.
• We have to wait because many people are lining up / queuing.

So vì introduces the reason.

A useful pattern is:

• [main clause] + vì + [reason]

Examples:

• Tôi ở nhà vì trời mưa. = I’m staying home because it’s raining.
• Cô ấy vui vì được nghỉ. = She is happy because she gets a break / is off work.

Người means person / people, and after nhiều (many), you can simply say:

• nhiều người = many people

You do not need a classifier here.

This is very natural Vietnamese.

Compare:

• một người = one person
• nhiều người = many people

Classifiers are important in many situations, but not every noun phrase needs one. After quantity words like nhiều, it is very common to say the noun directly.

Đang marks an action as in progress, similar to English be + -ing.

So:

• xếp hàng = line up / queue
• đang xếp hàng = are lining up / are queuing

In this sentence, it shows that the people are currently in the process of standing in line.

Compare:

• Nhiều người xếp hàng. = Many people line up / many people are in line
  (more general or context-dependent)
• Nhiều người đang xếp hàng. = Many people are lining up right now

Xếp hàng literally means something like arrange in a line.

Breakdown:

• xếp = arrange, place in order
• hàng = row, line

Together, xếp hàng means:

• to line up
• to stand in line
• to queue

So nhiều người đang xếp hàng means many people are queuing / standing in line.

Vietnamese does not mark tense the same way English does.

This sentence does not have a specific tense ending. Instead, time is understood from:

• context
• time words
• aspect markers like đang

Here:

• đang xếp hàng strongly suggests a present ongoing action
• phải đợi could be understood as have to wait, had to wait, or will have to wait, depending on context

So if you saw this sentence by itself, the most natural reading is probably:

• We have to wait because many people are queuing.

But in the right context, it could also refer to the past:

• We had to wait because many people were queuing.

If you want to make time clearer, Vietnamese can add words like:

• hôm qua = yesterday
• bây giờ = now
• ngày mai = tomorrow

Yes. The given word order is very normal:

• Chúng tôi phải đợi vì nhiều người đang xếp hàng.
• We have to wait because many people are queuing.

But the reason can also come first:

• Vì nhiều người đang xếp hàng, chúng tôi phải đợi.

That means the same thing:
Because many people are queuing, we have to wait.

So both orders are possible:

1. main statement + vì + reason
2. Vì + reason, main statement

The first one is often more conversational and straightforward.

Yes, it can be omitted, but the meaning becomes a bit less specifically ongoing right now.

Compare:

• nhiều người đang xếp hàng = many people are queuing right now
• nhiều người xếp hàng = many people queue / many people are in line, depending on context

In this sentence, đang helps paint a clearer picture of the situation happening at the moment, which is why it sounds natural.

Sometimes yes, if the subject is already obvious from context.

For example, in conversation, someone might say simply:

• Phải đợi vì nhiều người đang xếp hàng.
• Have to wait because many people are queuing.

That can sound natural if everyone already knows who has to wait.

However, including chúng tôi makes the sentence clearer and more complete, especially for learners or in stand-alone sentences.

It is natural and grammatical.

A native speaker would understand it easily as:

• We have to wait because many people are in line / queuing.

Depending on style, you might also hear close variations such as:

• Chúng tôi phải chờ vì nhiều người đang xếp hàng.
• Bọn tôi phải đợi vì có nhiều người đang xếp hàng.

But the original sentence is perfectly normal Vietnamese.