El sábado vamos a celebrar el cumpleaños de mi vecina, que cumple diecisiete y quiere una tarta sencilla.

In Spanish, days of the week often take the article el when you mean on a particular day or when talking about a regular day in general.

So El sábado vamos a celebrar... means On Saturday we’re going to celebrate...

A few useful comparisons:

• El sábado = on Saturday
• Los sábados = on Saturdays / every Saturday

Unlike English, Spanish often uses the article where English does not.

Vamos a + infinitive is a very common way to talk about the near future in everyday Spanish.

So:

• vamos a celebrar = we’re going to celebrate
• celebraremos = we will celebrate

Both are correct, but vamos a celebrar sounds very natural and conversational here. A learner should get used to this structure because it is extremely common in spoken Spanish.

This is the near future construction.

It is formed with:

• present tense of ir
• • a
• • infinitive

So here:

• vamos = we go / we are going
• a
• celebrar = to celebrate

Together: vamos a celebrar = we are going to celebrate

More examples:

• Voy a estudiar = I’m going to study
• Van a llegar tarde = They’re going to arrive late

Spanish normally expresses possession with de, where English often uses ’s.

So:

• el cumpleaños de mi vecina = my neighbour’s birthday
• literally: the birthday of my neighbour

This pattern is very common:

• la casa de Juan = Juan’s house
• el coche de mi hermano = my brother’s car

Spanish does not usually use an apostrophe-style possessive the way English does.

Vecina means female neighbour.

The masculine form is:

• vecino = male neighbour / neighbour (if masculine)

Since the person in the sentence is a woman or girl, Spanish uses the feminine noun:

• mi vecina

Notice that mi stays the same for masculine and feminine:

• mi vecino
• mi vecina

Here que means who.

In the sentence:

• mi vecina, que cumple diecisiete y quiere una tarta sencilla

it introduces extra information about mi vecina:

• my neighbour, who is turning seventeen and wants a simple cake

So this que is a relative pronoun.

It is connecting the noun mi vecina to more information about her.

The comma shows that the part after que is giving extra, non-essential information about mi vecina.

So:

• mi vecina, que cumple diecisiete...

means we already know which neighbour we mean, and now we are just adding more details about her.

This works like English:

• my neighbour, who is turning seventeen...

If the information were essential to identify the person, Spanish might omit the comma.

Both are possible.

• cumple diecisiete años = fully explicit
• cumple diecisiete = shorter, very natural

Spanish often omits años when the meaning is clear.

So cumplir diecisiete means to turn seventeen.

This is very common with birthdays and ages:

• Hoy cumple diez = He/She turns ten today
• Mi hermano cumplió treinta = My brother turned thirty

In this context, cumple diecisiete means turns seventeen.

The verb is cumplir, which has several meanings, but with ages and birthdays it often means:

• to turn an age
• or literally to complete an age/year

So:

• cumple diecisiete = she turns seventeen

Because the sentence is about a future celebration on Saturday, English might naturally translate it as is turning seventeen, even though Spanish simply uses cumple.

Because the wanting is treated as a current fact.

• quiere una tarta sencilla = she wants a simple cake

Her desire exists now, even if the celebration happens later.

This is very normal in both Spanish and English. We often use the present for something that is true now, even when it relates to a future event.

In Spain, tarta is a very common word for a cake, especially a celebration cake or one served as dessert.

Pastel can also mean cake, but usage varies by region, and in Spain tarta is often the most natural choice for a birthday cake.

So in this sentence:

• una tarta sencilla = a simple cake

For a learner of Spanish from Spain, tarta is a very useful word to remember for birthday cakes.

In Spanish, adjectives usually come after the noun.

So:

• una tarta sencilla = a simple cake

This is the normal word order:

• un coche rápido = a fast car
• una casa grande = a big house

Sometimes adjectives can come before the noun, but that often changes the tone or emphasis. Here tarta sencilla is the standard, neutral order.

Because adjectives in Spanish usually agree with the noun in gender and number.

• tarta is feminine singular
• so the adjective must also be feminine singular: sencilla

Compare:

• un pastel sencillo = masculine singular
• una tarta sencilla = feminine singular
• unas tartas sencillas = feminine plural

Yes. Celebrar el cumpleaños commonly means to celebrate someone’s birthday, and in practice that can include the party or gathering for it.

So the phrase does not separate those ideas very strictly. It simply means the birthday occasion is being celebrated.

Because mi vecina is not the direct object of the verb celebrar.

The direct object is:

• el cumpleaños

Then de mi vecina just tells us whose birthday it is.

So the structure is:

• celebrar
  • el cumpleaños
• de mi vecina

You would use the personal a with a direct object that is a specific person, for example:

• Vemos a mi vecina = We see my neighbour

But here it is:

• celebramos el cumpleaños de mi vecina

so no personal a is needed.

A very natural English version would be:

On Saturday we’re going to celebrate my neighbour’s birthday; she’s turning seventeen and wants a simple cake.

That helps show a few important differences from Spanish:

• El sábado = On Saturday
• vamos a celebrar = we’re going to celebrate
• el cumpleaños de mi vecina = my neighbour’s birthday
• que cumple diecisiete = who’s turning seventeen
• quiere una tarta sencilla = wants a simple cake