Learn Hardcore Spanish (Latin America): La silla sobre la que dejaste la sudadera es de mi hermana. - The chair on which you left the sweatshirt is my sister’s.

It’s a relative structure meaning “on which.” Spanish doesn’t allow the preposition to be left dangling at the end the way English does (“the chair you left the sweatshirt on”). Instead, the preposition must go in front of the relative pronoun: sobre la que = “on which.” It refers back to la silla and agrees with it in gender and number (feminine singular → la que).

Could I just say “La silla que dejaste la sudadera sobre”?

No. That copies English preposition stranding. In Spanish the preposition must come before the relative pronoun: La silla sobre la que dejaste la sudadera… A natural alternative is to avoid the relative altogether: Dejaste la sudadera sobre la silla de mi hermana.

Is “sobre” the only option? What about “en”?

Both are possible:

sobre = literally “on top of,” a bit more specific or formal.
en = very common for “in/on/at” in Latin America.

So you can say: La silla en la que dejaste la sudadera… It’s very natural in Latin America.

Can I use “donde” instead of “en la que/sobre la que”?

Yes, colloquially: La silla donde dejaste la sudadera… works because a chair is a location for the item. It’s a bit more informal/streamlined than en la que. Avoid adonde here; that’s for motion toward a place (with verbs like ir, llegar).

Why is it “la que” and not just “que”?

After most prepositions, Spanish uses either:

preposition + article + que: en la que, sobre la que
preposition + el/la cual: en la cual, sobre la cual (more formal)
sometimes preposition + que without article is fine (e.g., en que), but with sobre most speakers prefer the article: sobre la que sounds natural and clear.

“la” agrees with la silla (feminine singular).

What’s the difference between “la que” and “la cual” here?

Meaning is the same. La cual is more formal/literary: La silla sobre la cual dejaste la sudadera… In everyday speech, la que or en la que is more common.

Why is it “dejaste” (preterite) and not “has dejado” (present perfect)?

In Latin American Spanish, completed past actions are typically expressed with the preterite: dejaste. Has dejado is understood, but it’s used less often for recent past without a present connection than in Spain. If you want current relevance, you could say has dejado (“you have left [and it matters now]”).

Does “dejar” here mean “to allow” or “to leave (behind)”?

Here it means “to leave/leave behind/leave somewhere.” Context disambiguates:

Dejaste la sudadera en la silla = You left your sweatshirt on the chair.
Dejar + infinitive can mean “to allow/let”: Me dejaste salir = You let me go out.

Should it be “la sudadera” or “tu sudadera”?

Both are possible:

la sudadera assumes the sweatshirt is identifiable from context (already mentioned or obvious).
tu sudadera specifies it’s yours: …dejaste tu sudadera… Either works; pick what you want to emphasize.

Is “sudadera” the usual word in Latin America?

It’s widely understood and common (especially in Mexico/Central America) for “sweatshirt/hoodie.” Regional alternatives:

Argentina/Uruguay/Paraguay: buzo (sweatshirt); hoodie can be buzo con capucha.
Chile: polerón.
Colombia/Ecuador/Peru: buzo (can mean sweatshirt or sweater).
General “sweater” loanword: suéter.

So sudadera is fine, but you’ll hear others depending on the country.

Why is it “es de mi hermana” instead of using an apostrophe like English (“my sister’s”)?

Spanish expresses possession with de + possessor:

La silla … es de mi hermana = The chair … is my sister’s. Spanish doesn’t use the English ’s. Also, don’t add an article before mi here: not de la mi hermana; just de mi hermana.

Do I ever need the personal “a” with “mi hermana” here?

Not with ser de. But with pertenecer, you would: La silla … pertenece a mi hermana. With direct objects that are people, you also use the personal a (e.g., Vi a mi hermana), but that’s a different structure.

What is “la que” agreeing with, exactly?

With la silla (feminine singular). If the antecedent changes, agreement changes:

Plural: Las sillas sobre las que dejaste la sudadera… son de mi hermana.
Masculine: El escritorio sobre el que…

Do I need commas around the clause?

No, not here. It’s a restrictive clause specifying which chair. With commas, it becomes non‑restrictive (extra information): La silla, sobre la que dejaste la sudadera, es de mi hermana. That would imply there’s only one relevant chair and you’re adding a side note.

Can I rephrase to avoid “preposition + relative” altogether?

Yes. Two natural options:

Dejaste la sudadera en/sobre la silla de mi hermana.
Dejaste la sudadera en la silla que es de mi hermana. (The first is smoother.)

Is “silla” the same as “sillón” or “asiento”?

No:

silla = chair (typically with a back, one person, not cushy).
sillón = armchair (big, cushioned).
asiento = seat (the place to sit, e.g., on a bus, not necessarily a chair).

Why “mi” without an accent? When would it be “mí”?

mi (no accent) = “my” (possessive adjective): mi hermana.
mí (with accent) = “me” after a preposition: para mí, de mí. In the sentence it’s possession, so mi is correct.

Is “dejastes” ever correct?

Standard Spanish is tú dejaste (no final -s). Dejastes is a nonstandard form you may hear in some dialects but it’s not considered correct in formal or educated usage.