El muchacho abrió la puerta.

They are the Spanish definite articles, meaning the.

• el is used with singular masculine nouns: el muchacho
• la is used with singular feminine nouns: la puerta

In Spanish, articles usually have to agree with the noun’s gender and number.

Spanish nouns have grammatical gender.

• muchacho is masculine, so it takes el
• puerta is feminine, so it takes la

Very often, nouns ending in -o are masculine and nouns ending in -a are feminine, though there are exceptions. Here, both follow the common pattern.

Muchacho usually means boy, lad, or sometimes young man, depending on context.

In Spain, learners will also often hear chico for boy or guy. Muchacho is perfectly correct, but in everyday speech chico may be more common in some situations.

The accent mark shows the correct stress: a-brió.

It is also the third-person singular preterite form of abrir:

• yo abrí = I opened
• tú abriste = you opened
• él/ella abrió = he/she opened

So in this sentence, abrió means opened.

It is the preterite tense, which is used for a completed action in the past.

So abrió tells you that the opening happened as a finished event: the boy opened the door.

Yes. Abrir is a regular -ir verb in the preterite.

Its forms are:

• abrí
• abriste
• abrió
• abrimos
• abristeis
• abrieron

So abrió follows the normal pattern for regular -ir verbs.

Yes, Spanish often leaves out subject pronouns, but here El muchacho is not just a pronoun like he. It is a full noun phrase: the boy.

You could say simply Abrió la puerta if the context already makes it clear who opened it. Using El muchacho makes the subject explicit and clear.

This is the normal word order in Spanish: subject + verb + object.

• El muchacho = subject
• abrió = verb
• la puerta = direct object

So the structure is very similar to English: The boy opened the door.

La puerta is the direct object. It is the thing directly affected by the action of the verb.

The boy did the action, and the door is what was opened.

Because la puerta is a thing, not a person.

Spanish uses the personal a before a specific human direct object, for example:

• Veo a María = I see María

But with objects or things, there is normally no a:

• abrió la puerta
• cerró la ventana

A good approximate pronunciation is ah-BRYOH.

A few useful points:

• the stress is on the last syllable: brió
• the r is a single tap, not a long rolled rr
• the b in Spanish is softer than English b in many contexts

So abrió sounds smoother than an English speaker might expect.

Yes, Spanish can change word order for emphasis or style.

For example:

• El muchacho abrió la puerta = neutral, standard order
• La puerta la abrió el muchacho = emphasizes the door or contrasts who opened it

The original sentence is the most basic and natural version for a learner to start with.

Yes. In Spain, common alternatives include:

• chico = boy, guy
• joven = young person, young man

So you might also hear:

• El chico abrió la puerta

That sounds very natural too.