Assim que a entrega chegar, eu vou abrir o pacote na cozinha.

As soon as the delivery arrives, I am going to open the package in the kitchen.

Breakdown of Assim que a entrega chegar, eu vou abrir o pacote na cozinha.

• eu: I
• na: in
• ir: to go (future auxiliary)
• chegar: to arrive

Questions & Answers about Assim que a entrega chegar, eu vou abrir o pacote na cozinha.

What does assim que mean here?

Assim que is a fixed expression meaning as soon as or once. In this sentence, it introduces the idea that one action happens immediately after another. It is best learned as one chunk, not as separate words.

Why is it chegar and not chega?

Because after expressions like assim que, Portuguese usually uses the future subjunctive when talking about something that has not happened yet.

So Assim que a entrega chegar... means as soon as the delivery arrives...

This can be confusing because with many regular verbs, the future subjunctive looks exactly like the infinitive. That is what happens with chegar.

Here, chegar is not an infinitive in meaning. It is the verb form required after assim que for a future event.

Compare:

Assim que a entrega chegar, eu vou abrir o pacote.
future event

Quando a entrega chega, eu abro o pacote.
habitual/repeated situation

Why do we use eu vou abrir instead of abrirei?

Eu vou abrir is the very common ir + infinitive future, which is extremely natural in spoken Brazilian Portuguese.

So:

eu vou abrir = everyday spoken style
abrirei = more formal, more written, sometimes more literary

Both are grammatically correct, but vou abrir sounds more natural in normal conversation.