El passaport és important quan vas a l'aeroport.

El means the. In this sentence, Catalan is talking about the passport in a general, practical sense: the passport is an important thing when you go to the airport.

Using un passaport would mean a passport, which sounds less natural here unless you are emphasizing one passport among others.

So:

• El passaport és important = The passport is important
• Un passaport és important = A passport is important (possible, but less natural in this kind of general statement)

Catalan often uses the definite article in broad, general statements like this.

És is the 3rd person singular form of ser (to be), meaning is.

The accent is important because it distinguishes és from es:

• és = is
• es = a reflexive/object pronoun, like himself / herself / itself / each other, depending on context

So in this sentence:

• El passaport és important = The passport is important

The accent is not optional here.

Because important is a cognate: a word that looks very similar in both languages and has the same meaning.

In Catalan, important is an adjective. Here it agrees with passaport, which is masculine singular.

Forms:

• important = masculine singular
• important = feminine singular
• importants = masculine plural
• importants = feminine plural

So it only changes in the plural, not between masculine and feminine singular.

Examples:

• El passaport és important.
• La maleta és important.
• Els documents són importants.

Yes. Here vas means you go.

It is the 2nd person singular present tense of anar (to go):

• jo vaig = I go
• tu vas = you go
• ell/ella va = he/she goes
• nosaltres anem = we go
• vosaltres aneu = you all go
• ells/elles van = they go

So:

• quan vas a l'aeroport = when you go to the airport

Catalan often leaves out the subject pronoun, so tu vas is usually just vas.

Because Catalan usually omits subject pronouns when the verb already makes the subject clear.

So both are possible:

• quan vas a l'aeroport
• quan tu vas a l'aeroport

But the version without tu is more natural unless you want emphasis or contrast.

English normally needs the subject:

• when you go to the airport

Catalan often does not:

• quan vas a l'aeroport

This is because of apostrophe rules.

Normally:

• a + el = al

Example:

• Vaig al banc = I go to the bank

But when el comes before a vowel, it becomes l':

• el aeroport becomes l'aeroport

So after a, you get:

• a l'aeroport

Not:

• al aeroport

That is because the article is no longer el, but l' before the vowel.

The apostrophe shows that the article el has been shortened before a word beginning with a vowel.

• el + aeroport → l'aeroport

This is very common in Catalan.

Other examples:

• l'escola = the school
• l'home = the man
• l'hotel = the hotel

So l'aeroport simply means the airport.

Here quan means when.

In this sentence:

• quan vas a l'aeroport = when you go to the airport

It is a very common time word in Catalan.

Examples:

• Quan arribes? = When do you arrive?
• Truca'm quan puguis. = Call me when you can.

So yes, in many contexts quan translates directly as when.

Yes, that word order is also correct.

Both are natural:

• El passaport és important quan vas a l'aeroport.
• Quan vas a l'aeroport, el passaport és important.

The difference is mostly about focus:

• Starting with El passaport emphasizes the passport
• Starting with Quan vas a l'aeroport emphasizes the situation or time

Catalan is fairly flexible with word order, although the first version is very straightforward and neutral.

Yes, that is a very good thing to notice.

In Catalan, vas can be:

1. present tense of anar

   • tu vas = you go

2. Part of the periphrastic past

   • vas anar = you went

In this sentence, vas appears alone, not followed by an infinitive, so it means:

• you go

If it were past, you would expect something like:

• quan vas anar a l'aeroport = when you went to the airport

So here there is no real ambiguity.

Yes, aeroport is masculine, which is why the sentence uses el / l' rather than la.

You can tell from the article:

• el passaport
• l'aeroport (from el aeroport)

So:

• el / l' = masculine singular here
• la / l' would be feminine singular

As with many nouns, you often learn the gender together with the word:

• el passaport
• l'aeroport

That is the safest habit.

You would need to change both the noun and the article.

Singular:

• a l'aeroport = to the airport

Plural:

• als aeroports = to the airports

That is because:

• a + els = als

So:

• El passaport és important quan vas als aeroports.

This is grammatically correct, though semantically it sounds a bit less natural than the singular, because people more often say when you go to the airport as a general situation.

Almost, yes:

• El = the
• passaport = passport
• és = is
• important = important
• quan = when
• vas = you go
• a l'aeroport = to the airport

So the structure is very close to English:

• The passport is important when you go to the airport.

This is a nice example of a Catalan sentence that maps quite neatly onto English, even though the grammar details—like omitted tu and the apostrophe in l'aeroport—work differently.