Embora o porta-malas seja grande, minha irmã prefere ir de moto quando o dia está bonito.

Embora means although / even though, so it introduces a concession: one fact is true, but it does not change the result.

• Embora o porta-malas seja grande = Although the trunk is big
• mas = but

Both can connect contrasting ideas, but they work differently:

• Embora usually introduces a subordinate clause.
• Mas connects two more independent statements.

So this sentence is built as:

• Although the trunk is big, my sister prefers to go by motorcycle...

That is why embora is a very natural choice here.

Because embora normally requires the subjunctive in Portuguese.

So:

• embora ... seja = correct
• embora ... é = not correct in standard Portuguese

Here, seja is the present subjunctive form of ser.

This happens because embora introduces a clause with concession, and Portuguese generally uses the subjunctive after expressions like that.

A few examples:

• Embora ele esteja cansado, vai trabalhar.
• Embora seja tarde, ainda há gente na rua.

So in your sentence:

• Embora o porta-malas seja grande...

the subjunctive is required by embora.

Porta-malas means car trunk in Brazilian Portuguese.

It is a compound noun written with a hyphen. Literally, it comes from the idea of something that carries luggage.

A few useful points:

• o porta-malas = the trunk
• It is masculine
• The usual plural is also os porta-malas

Examples:

• O porta-malas do carro é pequeno.
• Os porta-malas desses carros são grandes.

So in your sentence, o porta-malas is simply the trunk.

Noun gender in Portuguese is often something you just have to learn with the word, and porta-malas is masculine: o porta-malas.

There is no simple rule from the ending here, because this is a compound noun. So it is best to memorize it as a full unit:

• o porta-malas

That said, this is very common in Portuguese learning: always learn nouns with their article.

• o carro
• a moto
• o porta-malas

That helps you remember gender naturally.

Yes, both are possible in Brazilian Portuguese:

• minha irmã
• a minha irmã

In Brazil, the article before a possessive is often optional, especially in many everyday contexts.

So these can both sound natural:

• Minha irmã prefere ir de moto.
• A minha irmã prefere ir de moto.

The version without the article can sound a little lighter or more direct, and it is very common.

Because preferir usually needs to be followed by:

• a noun: Ela prefere café.
• or an infinitive verb when you are talking about an action: Ela prefere ir de moto.

Here the preference is about what she prefers to do, not just about a thing. So Portuguese uses:

• prefere ir = prefers to go

You could also say:

• minha irmã prefere andar de moto

but that means something slightly closer to prefers riding a motorcycle. In your sentence, prefere ir de moto focuses on the means of going somewhere.

In Portuguese, means of transportation are often expressed with de:

• de carro = by car
• de ônibus = by bus
• de trem = by train
• de moto = by motorcycle

So:

• ir de moto = to go by motorcycle

If you say na moto, that usually means on the motorcycle in a more literal/spatial sense, not just the general means of transport.

And com a moto means with the motorcycle, which is a different idea.

So for transportation, de moto is the normal choice here.

Both can be correct, but they mean slightly different things.

In your sentence:

• quando o dia está bonito sounds like a habitual or general situation:
  • when the day/weather is nice
  • meaning this is what she tends to do whenever that condition happens

If you say:

• quando o dia estiver bonito

that sounds more like a future possibility:

• when the day is nice / when the weather turns out nice at some future time

So the original sentence gives a more general, repeated idea:

• although the trunk is big, she prefers going by motorcycle when the weather is nice

Yes, literally it means the day is beautiful, but in context it naturally means something like:

• the weather is nice
• it’s a nice day out

Portuguese often uses o dia está bonito to talk about pleasant weather.

Similar natural phrases are:

• Hoje o dia está lindo. = The weather is beautiful today.
• O dia está feio. = The weather is ugly / bad.

So although it is literally about the day, the intended meaning is usually about the weather or overall outdoor conditions.

Because bonito agrees with o dia, and dia is masculine:

• o dia → bonito
• a noite → bonita

So:

• o dia está bonito
• a tarde está bonita

The adjective has to match the noun in gender and number. Since dia is singular masculine, bonito is the correct form.

The comma separates the introductory embora clause from the main clause.

Structure:

• Embora o porta-malas seja grande, = subordinate concessive clause
• minha irmã prefere ir de moto... = main clause

When a clause beginning with embora comes first, using a comma before the main clause is standard and natural.

If you reversed the order, you could also write:

• Minha irmã prefere ir de moto quando o dia está bonito, embora o porta-malas seja grande.

So the comma helps show the sentence structure clearly.