¿Podría usted decirme si la de atrás está libre?

Podría is the conditional form of poder and makes the request sound more polite and less direct.

• ¿Puede usted decirme...? = Can you tell me...?
• ¿Podría usted decirme...? = Could you tell me...?

In English, could is often more polite than can, and the same idea applies here.

Usted is the formal word for you in Spanish. It is used to sound respectful, especially with:

• strangers
• staff
• older people
• formal situations

So ¿Podría usted decirme...? is a polite, formal way to speak.

In many situations, especially in Spain, usted can be omitted because the verb already shows the form:

• ¿Podría decirme si la de atrás está libre?

This still sounds polite.

Because me is an object pronoun attached to the infinitive decir.

• decir = to tell
• me = to me

So decirme literally means to tell me.

In Spanish, pronouns can be attached to an infinitive:

• decirme
• ayudarme
• explicarle

You could also sometimes restructure the sentence, but in this case decirme is the natural form.

Here si means whether.

• decirme si... = tell me whether...

In English, we often say:

• Could you tell me if the one at the back is free?

That if really means whether, not a condition.

So this is not a conditional if like If it rains.... It introduces an indirect yes/no question.

La de atrás means the one at the back. Spanish often uses el/la + de + place/description to avoid repeating a noun that is understood from context.

For example, if you are talking about chairs, seats, tables, parking spaces, etc., you can say:

• la de atrás = the one at the back
• la de la izquierda = the one on the left
• la azul = the blue one

The noun is omitted because both speakers already know what is being referred to.

Because the hidden noun is feminine.

For example, if the speaker means:

• la silla = the chair
• la mesa = the table
• la plaza = the seat/space

then la de atrás is correct.

If the omitted noun were masculine, you would use el:

• el de atrás = the one at the back

So the article agrees with the noun that is understood, even if the noun is not actually said.

De atrás means at the back, in the back, or the one behind, depending on context.

Literally, it is something like the one from the back, but in natural English we usually translate it as:

• the one at the back
• the one in back
• the one behind

It is a very common way to identify something by position.

Spanish uses estar for temporary states or current conditions, and ser for identity or more permanent characteristics.

Here libre means something like:

• available
• free
• unoccupied

That is a temporary condition, so Spanish uses estar:

• está libre = it is free/available

If you said es libre, it would usually mean something very different, more like:

• it is free by nature
• he/she is free
• it is unrestricted

So está libre is the correct choice here.

Yes, but in this context libre usually means available, empty, or unoccupied, not free of charge.

For example:

• ¿Está libre esta silla? = Is this chair free / is anyone using it?
• ¿Está libre esta mesa? = Is this table available?

So even though the literal translation may be free, the practical meaning is usually available.

The word order is natural and standard, but there is some flexibility.

• ¿Podría usted decirme si la de atrás está libre?
• ¿Podría decirme usted si la de atrás está libre?
• ¿Podría decirme si la de atrás está libre?

All of these are possible.

The most natural version in many situations is probably:

• ¿Podría decirme si la de atrás está libre?

Including usted makes the formality especially clear, but it is not required.

Yes, it sounds perfectly natural in Spain, especially in a polite situation such as asking about a seat, table, chair, or parking space.

A native speaker in Spain might also say slightly different versions depending on the context, such as:

• Perdone, ¿está libre la de atrás?
• ¿Me podría decir si la de atrás está libre?
• Disculpe, ¿está ocupada la de atrás?

But the original sentence is correct, polite, and natural.