La professora explica que demà hi ha un examen important.

Hi ha is the standard Catalan way to say there is / there are.

• ha by itself means has
• hi is a little word that helps create the existential meaning there is/are

So:

• hi ha un examen = there is an exam
• hi ha exàmens = there are exams

This is one of the most common fixed expressions in Catalan, so it is best learned as a chunk: hi ha.

In Catalan, just like in English, the present tense is often used for scheduled or near-future events when a time expression makes the future clear.

So demà hi ha un examen literally uses the present, but it means:

• Tomorrow there is an exam
• naturally: There’s an exam tomorrow

Because demà already shows the time, Catalan does not need a future tense here.

Que here means that and introduces a subordinate clause.

• La professora explica = The teacher explains / says
• que demà hi ha un examen important = that tomorrow there is an important exam

In English, that is often optional:

• The teacher explains that...
• The teacher explains...

In Catalan, que is normally kept in this structure.

It can feel a bit like both, depending on context.

The basic meaning of explicar is to explain, but in real usage it can also mean to tell or to say/explain that.

So in this sentence, La professora explica que... could be understood as:

• The teacher explains that...
• The teacher says that...
• The teacher tells us that...

The exact English wording depends on context, but the Catalan is completely natural.

Because professora refers to a female teacher.

• el professor = the male teacher
• la professora = the female teacher

The article also changes:

• la professora
• el professor

A learner may notice the ending -a, which often marks feminine nouns/adjectives in Catalan, though not always.

In Catalan, adjectives usually come after the noun.

So:

• un examen important = an important exam

This is the normal order:

• noun + adjective

Examples:

• una casa gran = a big house
• un llibre interessant = an interesting book

Some adjectives can come before the noun, but the usual basic pattern is after it.

The ending does not always tell you the gender.

Examen is a masculine noun, so it takes:

• un examen
• l’examen

You often have to learn noun gender together with the article. A good habit is to memorize nouns as a unit:

• un examen
• una classe
• el professor
• la professora

That will help more than trying to guess from the ending alone.

Demà means tomorrow.

It is an adverb of time. In this sentence, it tells you when the exam takes place:

• demà hi ha un examen important

You may also notice the accent mark: à. It is part of the correct spelling.

Yes. Catalan allows some flexibility with time expressions.

These are all natural or understandable:

• La professora explica que demà hi ha un examen important.
• La professora explica que hi ha un examen important demà.

The version with demà earlier in the clause often sounds a bit more neutral when the speaker is setting the time frame first.

Roughly:

• hi sounds like ee
• ha has a silent h

So hi ha is approximately ee a, though in natural speech the sounds run together smoothly.

A learner should especially remember:

• Catalan h is silent
• hi ha is very frequent, so its pronunciation becomes familiar quickly

Yes. Explica is the third person singular present form of the verb explicar.

• infinitive: explicar = to explain
• jo explico = I explain
• tu expliques = you explain
• ell/ella explica = he/she explains

So La professora explica... means The teacher explains...

Because demà is an adverb, not a noun here.

You do not say el demà in this sentence, just as in English you do not say the tomorrow.

It functions like:

• avui = today
• demà = tomorrow
• ahir = yesterday

These time words usually appear without an article when used as adverbs.