Quan fa calor, vull aigua i no vull cafè.

Quan means when here. It introduces a time clause: Quan fa calor = When it’s hot.

A learner might also see quan? as a question word meaning when?, but in this sentence it is being used to connect two parts of the sentence, not to ask a question.

Catalan often uses fer in weather and temperature expressions.

So:

• fa calor = it’s hot
• literally, it is something like it makes heat

This is just the normal Catalan expression. In the same way, you will also see:

• fa fred = it’s cold
• fa sol = it’s sunny
• fa vent = it’s windy

So fa calor is the standard way to say that the weather is hot.

Vull means I want. It is the 1st person singular form of the verb voler = to want.

A few useful forms are:

• vull = I want
• vols = you want
• vol = he/she/it wants
• volem = we want
• voleu = you all / you formal plural want
• volen = they want

So:

• vull aigua = I want water
• no vull cafè = I do not want coffee

Catalan usually leaves out the subject pronoun when it is already clear from the verb form.

Because vull already means I want, you do not need jo.

So both are possible:

• Vull aigua = I want water
• Jo vull aigua = I want water

But jo is usually added only for emphasis, contrast, or clarity.

In Catalan, the basic negative pattern is:

• no + verb

So:

• vull cafè = I want coffee
• no vull cafè = I do not want coffee

This is very regular in Catalan. The negative word no usually comes directly before the conjugated verb.

In Catalan, just like in English, you often leave out the article with food and drink when speaking in a general or indefinite way.

So:

• vull aigua = I want water
• no vull cafè = I don’t want coffee

You could use an article in some contexts, but it changes the feel:

• vull l’aigua = I want the water
• vull un cafè = I want a coffee

In your sentence, aigua and cafè are general substances/drinks, so no article is very natural.

Catalan often repeats the verb in coordinated clauses, especially when the meaning is I want X and I don’t want Y.

So:

• vull aigua i no vull cafè

sounds complete and natural.

You may sometimes hear shorter structures in conversation, but repeating the verb is the clearest and most standard form for learners.

I means and, and però means but.

In this sentence, i simply links two ideas:

• I want water
• I do not want coffee

That is perfectly natural in Catalan.

You could also say:

• Quan fa calor, vull aigua, però no vull cafè.

This would sound a bit more contrastive, like I want water, but I don’t want coffee. Both are possible; i is just simpler and more neutral.

The comma separates the introductory time clause from the main clause:

• Quan fa calor, = When it’s hot,
• vull aigua i no vull cafè. = I want water and I don’t want coffee.

This is similar to English punctuation when a dependent clause comes first. In short sentences, commas can sometimes vary a little in informal writing, but this comma is completely normal and helpful.

Yes, but the meaning changes.

• Quan fa calor = when the weather is hot
• Quan tinc calor = when I feel hot / when I am hot

So fa calor talks about the outside temperature in general, while tinc calor talks about your personal sensation.

Both are common, but they are not exactly the same.

Aigua is pronounced approximately like EYE-gwuh.

A rough guide:

• ai sounds like the eye in English
• gu here gives a gw sound
• the final a is a short unstressed vowel

So: EYE-gwuh

Pronunciation can vary somewhat by dialect, but that approximation is good for a beginner.

The accent in cafè shows where the stress falls.

• cafè is stressed on the last syllable: ca-FÈ

Without the accent, the stress rules of Catalan would suggest a different pronunciation. So the accent is important both for spelling and for pronunciation.

In this sentence, cafè means coffee.

Catalan cafè can mean:

• coffee as a drink
• sometimes café / coffee shop, depending on context

But in vull aigua i no vull cafè, it clearly means the drink, because it is being contrasted with aigua.

Yes, Catalan has some flexibility, but the original order is the most natural and neutral for a learner.

Standard order here is:

• Quan fa calor, vull aigua i no vull cafè.

You could rearrange parts for emphasis, but that is more advanced. If you are learning, the safest pattern is:

1. time clause
2. main clause
3. negative no before the verb

So the sentence as given is a very good model to follow.