Learn Hardcore Portuguese (Brazil): O sinal do celular no aeroporto é fraco, por isso é melhor confirmar antes. - The cell phone signal at the airport is weak, so it's better to confirm beforehand.

Sinal do celular literally means “cell phone signal.” Here sinal = “signal” and celular = “cell phone” or “mobile phone,” so together it refers to the reception strength your phone gets.

Why is there do in sinal do celular instead of just de?

Do is the contraction of de + o (“of the”). Portuguese often contracts prepositions with definite articles. So sinal do celular = sinal de + o celular.

Why do we say o sinal with an article? In English we’d say “cell phone signal” without “the.”

Portuguese normally uses definite articles (o, a) before nouns, even in general statements. O sinal here is referring to the signal in a specific context (the airport), so the article o is required.

What does no aeroporto mean, and why no?

No is again a contraction, this time of em + o (“in the”). So no aeroporto means “in the airport.” Portuguese regularly uses em + o/a → no/na for locations.

Why is no aeroporto placed after sinal do celular? Could it go first?

Yes. Word order in Portuguese is relatively flexible. You could say No aeroporto o sinal do celular é fraco. Placing no aeroporto first just shifts the emphasis onto location.

What does fraco mean here?

Fraco means “weak” or “poor” when talking about a signal, i.e. “The cell phone signal is weak.”

What is the function of por isso, and why is it followed by a comma?

Por isso means “therefore,” “so,” or “because of that.” It links the first clause (“the signal is weak”) to the result/suggestion (“it’s better to confirm”). The comma marks that transition.

Why do we use the infinitive confirmar after é melhor?

Portuguese commonly uses é melhor + infinitive to give advice or say what’s best: “it’s better to do something.” The verb stays in the infinitive, not conjugated.

What does antes refer to? It just says “before.” Before what?

Antes here means “beforehand” or “before you go/check in/etc.” The specific action is implied by context—whatever you need to confirm (reservation, flight details, etc.).

Could we replace por isso with então or logo?

Yes. Então and logo also mean “so”/“therefore.” For example: “O sinal do celular no aeroporto é fraco, então é melhor confirmar antes.” The nuance is small—por isso is slightly more formal/written.

Is the comma before por isso mandatory?

In most cases, yes. When you start a result clause with por isso, you separate it with a comma: [cause], por isso [effect]. In speech you might pause naturally, but in writing the comma is standard.

Could I say é melhor confirmar antes no aeroporto?

You could, but it shifts the meaning: that you should confirm once you’re at the airport (not beforehand). The original antes is general/pre-activity. If you want “confirm while at the airport,” you’d specify lá no aeroporto.