Quan tinc febre, no vull sopar.

In Catalan, quan means when, and with the present tense it often expresses a general or habitual situation.

So Quan tinc febre, no vull sopar means something like:

• When I have a fever, I don’t want dinner
• or more naturally in English, Whenever I have a fever, I don’t want to eat dinner

The present tense in both parts of the sentence gives it a general, repeated meaning, not just something happening right now.

Catalan uses tenir (to have) for many physical states and conditions where English often uses to be or to have depending on the expression.

So:

• tenir febre = to have a fever
• tenir gana = to be hungry
• tenir set = to be thirsty
• tenir por = to be afraid

That means tinc febre is the normal Catalan way to say I have a fever.

In this expression, Catalan normally says tenir febre without an article.

So the usual form is:

• tinc febre = I have a fever

Using la would sound different and is not the basic everyday expression here. For a learner, the safest pattern is simply to remember:

• tenir febre
• not usually tenir la febre

Catalan often drops subject pronouns because the verb ending already shows who the subject is.

Here:

• tinc = I have
• vull = I want

So jo is unnecessary unless you want emphasis or contrast.

Compare:

• Quan tinc febre, no vull sopar. = normal
• Quan jo tinc febre, no vull sopar. = more emphatic, like When I have a fever...

This is very common in Catalan.

Catalan forms negation more simply than English in this case. You usually just put no before the conjugated verb.

So:

• vull = I want
• no vull = I do not want / I don’t want

There is no equivalent of English do-support here. That means:

• No vull sopar = I don’t want to eat dinner

Vull is the first-person singular form of the verb voler (to want). This verb is irregular, so its forms do not follow a completely predictable pattern.

Some useful forms are:

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

So vull is simply the correct irregular form for I want.

Because after voler (to want), Catalan usually uses another verb in the infinitive.

So:

• vull sopar = I want to have dinner / I want to eat dinner

This works like English want + to + verb, except Catalan does not need a separate word like to before the second verb.

More examples:

• vull dormir = I want to sleep
• vull menjar = I want to eat
• vull sortir = I want to go out

It can be either, depending on context.

• As a verb, sopar = to have dinner / to eat dinner
• As a noun, sopar = dinner / supper

In your sentence, it is clearly a verb because it comes after vull:

• vull sopar = I want to have dinner

If it were a noun, you would usually see something like:

• el sopar = the dinner / dinner

The comma is normal and helpful here because the sentence begins with a subordinate clause:

• Quan tinc febre, ...

It separates the when-clause from the main clause:

• Quan tinc febre, no vull sopar.

In informal writing, people may sometimes omit it, but using the comma is a good habit, especially for learners.

Not usually. The sentence is most naturally understood as a general statement or habitual truth:

• Whenever I have a fever, I don’t want to eat dinner

If you wanted to make it clearly about right now, Catalan would usually add more context, such as:

• Ara que tinc febre, no vull sopar. = Now that I have a fever, I don’t want dinner.

So your original sentence is best understood as a repeated or typical situation.