Al final de la obra, el público dio un gran aplauso.

Al final is the normal Spanish expression for at the end or in the end in this kind of sentence.

• al = contraction of a + el
• al final de la obra = at the end of the play

For events, stories, films, books, etc., Spanish usually prefers al final de...

Examples:

• Al final de la película, todos lloraron.
• Al final del concierto, hubo otra canción.

En el final is much less common here and can sound unnatural in many contexts.

Here, obra means play, as in a theatrical performance.

So:

• la obra = the play

But obra can also mean other things depending on context, such as:

• work or piece of work: una obra de arte = a work of art
• construction work: hay obras en la calle = there is roadwork / construction on the street

In this sentence, because of el público and aplauso, the meaning is clearly the play.

Because obra is a feminine noun:

• la obra
• therefore de la obra

Spanish only contracts:

• a + el = al
• de + el = del

But since the noun is feminine (la), there is no contraction:

• de la is correct
• del obra is incorrect

Because público here is a collective noun. It refers to a group of people as one unit: the audience.

So even though the audience contains many individuals, Spanish treats el público as grammatically singular.

That is why the sentence says:

• el público dio not
• el público dieron

This is similar to English the audience gave a big round of applause, where audience is also a singular collective noun.

Because the subject is el público, which is singular.

• el público = singular noun
• dio = third person singular of dar in the preterite

So:

• el público dio un gran aplauso = the audience gave a big round of applause

If the subject were plural, the verb would also be plural:

• Los espectadores dieron un gran aplauso.

Dio is the preterite form of dar.

• infinitive: dar
• preterite, third person singular: dio

The preterite is used because this is a completed action in the past:

• the applause happened once, at a specific moment, and finished

So dio fits very well.

Compare:

• dio un aplauso = gave applause / applauded at that moment
• daba un aplauso = was giving applause / used to give applause, depending on context

Here, the applause is a single completed event at the end of the play, so the preterite is the natural choice.

Spanish often uses the structure dar + noun where English might prefer a single verb.

So:

• dar un aplauso = to give applause / to give a round of applause
• aplaudir = to applaud

Both are possible, but they are not exactly identical in feel.

• El público dio un gran aplauso sounds a bit more like the audience gave a big round of applause
• El público aplaudió mucho means the audience applauded a lot

The version with dar un aplauso focuses more on the applause as a single event or gesture.

Un gran aplauso means a big applause, more naturally in English a big round of applause or loud applause.

• un aplauso = applause / a round of applause
• gran = great / big

In Spanish, aplauso is often used in the singular to refer to an instance of applause.

Examples:

• Recibió un aplauso. = He/She received applause.
• Recibió un gran aplauso. = He/She received a big round of applause.

Both come from the same adjective, but the form changes depending on position.

Before a singular noun:

• grande usually becomes gran
• un gran aplauso

After the noun:

• un aplauso grande

In many cases, gran before the noun sounds more natural and often feels a bit more idiomatic.

Also, adjective position can slightly affect nuance:

• un gran aplauso = a great/big round of applause
• un aplauso grande = a large/big applause, which sounds less natural here

So un gran aplauso is the standard phrasing.

The comma separates the introductory time phrase from the main clause.

• Al final de la obra, = introductory phrase
• el público dio un gran aplauso. = main clause

This is very similar to English:

• At the end of the play, the audience gave a big round of applause.

In short:

• the comma is natural and helpful
• it is especially common when the introductory phrase comes first

Yes, you may see it without the comma, and it is still understandable. But with the comma, it is usually better written style because Al final de la obra is an introductory phrase.

So:

• Al final de la obra, el público dio un gran aplauso. = more standard punctuation
• Al final de la obra el público dio un gran aplauso. = possible, but less polished

Yes, al final can sometimes mean in the end, depending on context. But in this sentence, because we have de la obra, it clearly means at the end of the play.

Compare:

• Al final de la obra = at the end of the play
• Al final, no fue = in the end, he/she didn’t go

So here the phrase is about a literal point in time during the play, not a general conclusion.

Yes, but el público is the more natural and common choice in many contexts for the audience.

• el público = the audience / the public
• la audiencia can also mean audience, but it can sometimes sound more formal or be used in media, broadcasting, or legal contexts depending on the situation

For a theatre audience, el público is very natural:

• Al final de la obra, el público dio un gran aplauso.

A close word-for-word breakdown is:

• Al final = at the end
• de la obra = of the play
• el público = the audience
• dio = gave
• un gran aplauso = a big round of applause

So the structure is:

At the end of the play, the audience gave a big round of applause.

This is a good example of Spanish using a structure very similar to English, except for the common expression dar un aplauso.