La motxilla no és a sota del llit; és a sobre.

La is the feminine singular definite article, meaning the.

• motxilla = backpack
• la motxilla = the backpack

In Catalan, you normally use the article with a specific noun like this.

Yes, motxilla is feminine, so it takes la.

There is not always a perfect rule, but nouns ending in -a are often feminine in Catalan. So:

• la motxilla
• una motxilla

You usually have to learn the gender along with the noun.

This is a very common question for English speakers, especially if they also know Spanish.

In Catalan, ser is often used for location in ways that may feel unusual if you are expecting Spanish-like usage. So La motxilla és a sota del llit is normal Catalan.

A simple learner-friendly way to think about it is:

• és = is
• here it is being used to say where the backpack is

So the sentence is perfectly natural as written. In some contexts or varieties, you may also hear estar, but és here is standard and very common.

A sota de is an expression meaning under or underneath.

So:

• a sota del llit
• literally: underneath of-the bed
• natural English: under the bed

The key part is:

• a sota de = under / underneath

When followed by el llit, de + el becomes del, giving a sota del llit.

Because de + el contracts to del in Catalan.

So:

• de + el llit → del llit

This is exactly the same kind of contraction you see in:

• al = a + el
• del = de + el

Since llit is masculine singular, it uses el, and the contraction is required.

Here a sobre means on top or above.

Because the first clause already mentions the bed, the second clause does not need to repeat it. So:

• és a sobre
• literally: it is above / on top
• understood meaning: it is on top of the bed or above it

The exact English translation can depend on context, but the idea is that the backpack is not underneath; it is up above instead.

Because Catalan, like English, often leaves out repeated information when it is already clear from context.

The full version could be:

• La motxilla no és a sota del llit; és a sobre del llit.

But that sounds more repetitive. Once del llit has already been said, és a sobre is enough.

In this sentence, a sobre is an adverbial expression meaning on top or above.

That is different from plain sobre, which often means:

• about / regarding
• or, in some contexts, on / over

For a learner, the safest takeaway is:

• a sota de = under
• a sobre de = on top of / above

And when no noun follows, you can just say:

• a sota
• a sobre

Yes. A very natural alternative is:

• La motxilla no és a sota del llit, sinó a sobre.

Sinó is used after a negative statement to correct it with the right alternative: not X, but Y.

So these two are very close in meaning:

• La motxilla no és a sota del llit; és a sobre.
• La motxilla no és a sota del llit, sinó a sobre.

The version with the semicolon repeats és, which makes the contrast slightly more explicit.

Yes, that is possible.

Both of these can mean under the bed:

• sota el llit
• a sota del llit

Similarly, for on top of / above the bed, Catalan may use forms like:

• a sobre del llit
• damunt del llit

So the sentence you were given is not the only possible way to express the idea, but it is a very normal one.

A helpful approximation for English speakers is:

• motxilla ≈ mo-CHEE-lya
• llit ≈ lyit

A few useful sound notes:

• tx sounds like English ch
• ll is a palatal sound, often approximated as ly
• llit is a short word, and the final t is pronounced

Pronunciation varies somewhat by dialect, but those approximations are a good starting point.