Learn Hardcore Spanish (Spain): Mi hermana va a estudiar en la biblioteca esta tarde. - My sister is going to study in the library this afternoon.

It’s the periphrastic future: ir (conjugated) + a + infinitive.
Here, va is the 3rd person singular of ir (to go), and estudiar is the infinitive.
It means “is going to study” (a planned or likely future action).
Full present-tense forms of ir: voy, vas, va, vamos, vais, van.

Can I say estudiará instead of va a estudiar?

Yes: Mi hermana estudiará en la biblioteca esta tarde is grammatically correct.
Nuance: va a estudiar often feels more immediate or planned; estudiará can sound a bit more formal or predictive. In everyday speech, the ir a + infinitive form is very common for near future.

Could I use the present tense to talk about the future here?

Yes: Mi hermana estudia en la biblioteca esta tarde is natural if the plan is fixed (like a schedule).
Spanish often uses the present with a future time expression for planned events.

Why is there an a after va? Can I say va estudiar?

Why is it en la biblioteca and not a la biblioteca?

en = in/at (location): estudiar en la biblioteca = to study at the library.
a = to (movement): ir a la biblioteca = to go to the library.
If you mean “She is going to the library to study,” say: Mi hermana va a la biblioteca a estudiar esta tarde.
Your sentence states where the studying will take place, not the movement to get there.

Do I need the article la before biblioteca?

Yes, typically: en la biblioteca. Spanish usually uses the definite article with places.
en biblioteca sounds odd in standard Spanish.
Use una biblioteca if you mean any library, not a specific/known one.

What’s the difference between biblioteca and librería?

biblioteca = library (you borrow books).
librería = bookshop/bookstore (you buy books).
Don’t mix them up: estudiar en la librería would mean “study at the bookstore.”

What does esta tarde mean exactly in Spain? Where’s the boundary with noche?

esta tarde = this afternoon/early evening (later today).
In Spain, tarde roughly runs from after lunch (around 2–3 p.m.) until nightfall/dinnertime (around 9–10 p.m., varies).
After that, it’s noche (night). If it’s late night, use esta noche.

What’s the difference between esta tarde and por la tarde?

esta tarde = this specific afternoon (today).
por la tarde = in the afternoon (in general/unspecified or habitually).
Spain typically says por la tarde, not en la tarde (the latter is more Latin American in some areas).

Why is esta written without an accent? What about está and ésta?

esta (no accent) = this (feminine demonstrative adjective): esta tarde.
está (accent) = is (3rd person of estar): Ella está cansada.
ésta (accent) used to be the pronoun “this one,” but the RAE now generally recommends no accent unless needed to avoid ambiguity.

Why is it mi without an accent and not mí?

Do I need to say ella? Could I say Ella va a estudiar…?

You can, but it’s not necessary. Spanish drops subject pronouns when context is clear.
Here the subject is explicit: Mi hermana. Saying Ella as well would be redundant unless you want emphasis or contrast.

How would this change if I talk about my brother or multiple siblings?

Where does the negation go? How do I say “is not going to study…”?

Place no before the conjugated verb: Mi hermana no va a estudiar en la biblioteca esta tarde.
If you add another negative idea: Mi hermana no va a estudiar en la biblioteca esta tarde tampoco (also fine to place tampoco earlier depending on emphasis).

Can I move esta tarde to another position?

Yes. All are fine, with slight shifts in emphasis:
- Mi hermana va a estudiar en la biblioteca esta tarde.
- Esta tarde, mi hermana va a estudiar en la biblioteca.
- Mi hermana, esta tarde, va a estudiar en la biblioteca. (more marked/style-driven)
Spanish is flexible with time expressions.

Is there any contraction needed with the adjacent vowels in va a estudiar?

No contraction. You pronounce the two a’s across the word boundary, often linking them smoothly.
The only common contraction here would be with a + el = al, but that doesn’t occur in this sentence.
Example with contraction: Va al gimnasio a estudiar (to show form), but your sentence uses en la biblioteca.

How is estudiar stressed and pronounced?

estudiar is stressed on the last syllable: es-tu-di-ar.
The d is a soft dental; the final -r in Spain is pronounced clearly but not rolled strongly (that’s rr).

Could the sentence be ambiguous between “is going to study” (future) and “is going (somewhere) to study”?

As written, va a estudiar en la biblioteca primarily reads as the future periphrasis (“is going to study”) and states the place of the action.
If you want to emphasize the physical movement to the library for the purpose of studying, use: Va a la biblioteca a estudiar (esta tarde).