Su mochila está en la silla.

Su is a possessive adjective meaning his, her, your (formal), or their.

So su mochila could mean:

• his backpack
• her backpack
• your backpack (if speaking formally to one person)
• their backpack
• your backpack (formal plural in some contexts)

Spanish often leaves this ambiguous unless the context makes it clear.

Spanish does not usually separate possession by the owner’s gender in this form. English distinguishes:

• his
• her

But Spanish uses su for both.

If you need to clarify, Spanish can add more information:

• Su mochila de él = his backpack
• Su mochila de ella = her backpack

In normal conversation, context usually makes this unnecessary.

Spanish uses estar for location.

So:

• La mochila está en la silla. = The backpack is on/in the chair.

Even though the backpack may stay there for a while, location is normally expressed with estar, not ser.

A simple rule:

• ser = identity, origin, characteristics
• estar = location, condition, state

The accent mark shows both pronunciation and meaning.

• está = he/she/it is or you are (formal), from estar
• esta = this (feminine), as in esta silla = this chair

So the accent helps distinguish the verb form from the demonstrative word.

Because both nouns are feminine in Spanish:

• la mochila
• la silla

In Spanish, nouns have grammatical gender, and articles must match:

• masculine singular: el
• feminine singular: la

This does not mean the objects are biologically female. It is just a grammar category.

Spanish often uses the definite article more broadly than English does.

So en la silla is very natural, even in cases where English might say:

• on the chair
• on a chair
• sometimes just on chair is impossible in English, but Spanish still needs an article

Here, la silla sounds completely normal. Context decides whether it feels more like the chair or simply the relevant chair in the situation.

En can mean both in and on, depending on context.

So:

• en la silla can mean on the chair

Spanish often uses en where English uses on for position with furniture or locations.

You may also hear sobre for on top of, but en la silla is very common and natural here.

Yes. Sobre la silla is possible and means on the chair / on top of the chair.

The difference is often:

• en la silla = neutral, very common for location
• sobre la silla = emphasizes physical position on top of the chair a bit more

In everyday speech, en la silla is often the more natural choice for this sentence.

In most of Latin America, silla is pronounced roughly like SEE-ya.

A simple breakdown:

• si = like see
• lla = usually like ya

So:

• silla ≈ SEE-ya

Depending on the region, the ll sound can vary a little, but y is a good practical pronunciation for most learners.

Yes. Mochila usually means backpack, but it can also refer more generally to a bag carried on the back, such as a school backpack or travel backpack.

In many Latin American contexts, mochila is the standard everyday word for backpack.

Yes. La mochila está en la silla is also correct.

The difference is:

• Su mochila = someone’s backpack
• La mochila = the backpack

Use su when you want to show who it belongs to. Use la when the backpack is already known from context and ownership is not important.

Not usually. Spanish often relies on context.

If everyone already knows whose backpack you mean, su mochila is enough. If there could be confusion, you can clarify:

• La mochila de Ana está en la silla.
• Su mochila de ella está en la silla. (possible, but less common than using the person’s name)

Most of the time, context solves the ambiguity naturally.