Learn Hardcore Vietnamese: Hôm qua trời mưa, nên chúng tôi không chơi ở công viên. - Yesterday it rained, so we did not play in the park.

Hôm qua means “yesterday.” In Vietnamese, it’s very common to put time indicators (yesterday, today, tomorrow) at the start of a sentence to establish the time frame before stating what happened.

Why isn’t there a past-tense marker like đã in this sentence?

Vietnamese does not require a separate past-tense verb like English “rained.” The time expression Hôm qua already tells you it’s past. Adding đã (the general marker for past) would be grammatical but redundant here: “Hôm qua trời đã mưa” is also correct but sounds a bit more formal or emphatic.

What is the subject of the second clause, and why is chúng tôi used?

In the clause “nên chúng tôi không chơi ở công viên,” chúng tôi (“we” or “us”) is the subject. Vietnamese distinguishes between chúng tôi (exclusive “we,” excluding the person you’re talking to) and chúng ta (inclusive “we,” including the listener). Here chúng tôi implies “we” did something without the listener.

What does nên do in this sentence?

Nên functions like “so” or “therefore.” It links the cause (it rained) to the result (we didn’t play). It marks a logical or causal relationship between the two clauses.

Why is không chơi used to express negation, and why does không come before chơi?

In Vietnamese, to negate a verb or adjective you place không before it. Here không chơi means “did not play.” Always put không directly in front of the verb it negates.

Why does the sentence say chơi ở công viên with ở, and can we omit ở?

Ở is a preposition meaning “at” or “in” when indicating location. You need chơi ở công viên to mean “play at the park.” Omitting ở and saying chơi công viên would sound unnatural—Vietnamese needs that preposition for clear location reference.

Why is there a comma before nên?

In written Vietnamese, a comma often separates clauses—especially a cause clause from its effect clause. Here the comma before nên marks the pause between “it rained” and “so we didn’t play.”

How does the cause-and-effect structure work with nên?

The typical pattern is: [Cause clause], nên [Result clause]. You describe the cause first (trời mưa), insert a comma, then nên to introduce what happened because of that cause (chúng tôi không chơi ở công viên).