Si no plou en una setmana, el bosc queda molt sec.

Ploure (to rain) is normally an impersonal verb in Catalan, just like to rain in English. That means it is usually used without a subject pronoun.

• plou = it rains / it is raining
• You do not normally say ell plou

Catalan often leaves out subject pronouns anyway, but with weather verbs like ploure, there is usually no real subject to express.

Catalan often uses the present tense to talk about general truths, habits, and natural consequences.

So this sentence means something like:

• whenever / if it doesn’t rain for a week, the forest gets very dry

This is similar to English sentences like:

• If it doesn’t rain, the ground gets dry.

It is not necessarily talking about one specific future event; it can describe a general pattern.

Here, si means if and no means not.

So:

• si no plou = if it doesn’t rain

Be careful not to confuse this with sinó, written as one word, which usually means but rather / except.

Compare:

• si no plou = if it doesn’t rain
• no és verd, sinó blau = it isn’t green, but rather blue

So in your sentence, it must be si no as two words.

This is a good question because the phrase can feel a bit different from English.

In this sentence, en una setmana suggests the idea of within the span of a week / over the course of a week. In natural English, the meaning is often expressed as:

• if it doesn’t rain for a week
• or if there is no rain in a week

Catalan can use en with time expressions in ways that do not match English word-for-word.

A nearby alternative would be:

• durant una setmana = for a week / during a week

But in your sentence, en una setmana is a natural way to express that time frame.

Here quedar means something like to become, to end up, or to be left in a state.

So:

• el bosc queda molt sec = the forest becomes very dry / ends up very dry

This use of quedar is common when talking about the resulting state of something.

Compare:

• La roba queda molla. = The clothes end up wet.
• La terra queda dura. = The soil becomes hard.

In this sentence, queda emphasizes the result after the lack of rain.

Yes, sometimes, but the nuance changes slightly.

• queda sec often emphasizes the resulting condition
• es torna sec = becomes dry, often a bit more neutral
• es posa sec can also mean gets dry, though it may sound less natural in some contexts

In this sentence, queda molt sec sounds very natural because it highlights the forest being left in a very dry state after no rain.

Because sec agrees with el bosc, which is masculine singular.

• el bosc = masculine singular
• therefore: sec

If the noun were feminine, you would use seca:

• la terra queda molt seca = the ground becomes very dry

So the adjective must match the noun in gender and number.

Because the sentence begins with the if-clause:

• Si no plou en una setmana, ...

After that introductory subordinate clause, Catalan commonly uses a comma before the main clause:

• Si no plou en una setmana, el bosc queda molt sec.

This works much like English:

• If it doesn’t rain for a week, the forest gets very dry.

If the order were reversed, the comma would often disappear:

• El bosc queda molt sec si no plou en una setmana.

Catalan uses the definite article quite often, including in cases where English may or may not use the.

Here el bosc means the forest. It refers to the forest as a known or relevant thing in the situation.

Catalan generally prefers the article with nouns more than English does in some contexts, so learners should get used to seeing articles frequently.

Molt means very in this sentence.

So:

• molt sec = very dry

It is an adverb modifying the adjective sec.

Compare:

• molt gran = very big
• molt humit = very humid
• molt fred = very cold

It describes a resulting state in that situation, not necessarily something permanent.

The idea is:

• after a week without rain, the forest gets / becomes very dry

That dryness could later change if it rains again. So queda here is about what state the forest ends up in, not about a permanent characteristic.

Yes. A common alternative is:

• El bosc queda molt sec si no plou en una setmana.

This means the same thing. The main difference is focus and flow:

• Si no plou en una setmana, ... puts the condition first
• El bosc queda molt sec ... puts the result first

Both are grammatical and natural.