Salió tras cerrar la puerta.

Salió is the third-person singular preterite of salir.

In this sentence, it means he/she/it left or he/she went out.

So depending on context, Salió could mean:

• He left
• She left
• He went out
• She went out
• You left / You went out (if speaking formally to usted)

Spanish often leaves the subject unstated, so the exact person depends on context.

Because Spanish is a pro-drop language, which means subject pronouns are often omitted when the verb already shows who the subject is.

Here, salió already tells you it is third-person singular:

• él salió
• ella salió
• usted salió

So Spanish normally just says Salió unless the speaker wants to add the pronoun for emphasis or clarity.

Salió is in the preterite tense.

The preterite is used for a completed action in the past. Here, the person left at a specific moment, so the action is viewed as finished.

Compare:

• Salió = he/she left / went out → completed event
• Salía = he/she was leaving / used to leave → ongoing, background, or habitual action

In this sentence, the action is a single completed event, so salió is the natural choice.

The accent mark shows the correct stress: sa-LIÓ.

This is the preterite form of salir:

• yo salí
• tú saliste
• él/ella/usted salió

The written accent is necessary in standard Spanish spelling. Without it, salio would be incorrect.

Tras means after here.

So:

• tras cerrar la puerta = after closing the door

In Spanish, tras can also mean behind in other contexts, but in this sentence it clearly means after.

This use is completely correct, though it can sound a little more formal or literary than some alternatives.

Because after a preposition like tras, Spanish normally uses the infinitive.

So:

• tras cerrar la puerta = after closing the door

This is the standard structure:

• tras + infinitive
• después de + infinitive
• antes de + infinitive

Examples:

• Después de comer, salió. = After eating, he/she left.
• Antes de entrar, llamó. = Before entering, he/she called.

So tras cerrar is grammatical because cerrar is the infinitive.

Yes. That is a very common alternative.

These are both correct:

• Salió tras cerrar la puerta.
• Salió después de cerrar la puerta.

They mean essentially the same thing.

A useful nuance:

• después de is usually more common in everyday speech
• tras can sound a bit more concise, formal, or literary, though it is still perfectly natural

La puerta refers to a specific door, one that is understood from the situation or context.

Spanish often uses the definite article when the object is identifiable:

• cerrar la puerta = close the door

This is very natural if both speaker and listener know which door is meant, which is usually the case.

If you said una puerta, it would sound more like a door, with no specific door in mind.

Yes, the structure strongly suggests that the subject of salió is also the understood subject of cerrar.

So the sentence naturally means:

• He/She left after closing the door

In other words, the same person both:

1. closed the door
2. left

If you wanted to make it clear that someone else closed the door, Spanish would normally need a different structure.

Yes. Salir covers both ideas.

Depending on context:

• salió de casa = he/she left the house
• salió del cuarto = he/she went out of the room
• salió del país = he/she left the country

In your sentence, either left or went out may work in English, depending on what the wider context is.

Yes. Spanish allows some flexibility.

You can also say:

• Tras cerrar la puerta, salió.

This means the same thing. The difference is mainly one of focus or style:

• Salió tras cerrar la puerta. puts the main action left first
• Tras cerrar la puerta, salió. foregrounds the after closing the door part first

Both are correct and natural.

It expresses time, not reason.

It tells you the sequence of events:

1. the door was closed
2. then the person left

So it means after closing the door, not because of closing the door.

If you wanted to express reason, Spanish would normally use a different structure, such as porque or another causal expression.