A la motxilla no hi cap la tovallola gran.

Here cap comes from the verb cabre, which means to fit or to have enough room.

So:

• hi cap = it fits there / there is room for it there
• no hi cap = it doesn’t fit there

In this sentence, cap is third person singular present, because the thing that does or doesn’t fit is la tovallola gran.

A useful comparison:

• La tovallola hi cap. = The towel fits in there.
• La tovallola no hi cap. = The towel doesn’t fit in there.

Hi is a locative pronoun. It refers to a place, roughly like there / in it / in there.

In this sentence, it refers to a la motxilla:

• A la motxilla = in the backpack / in the backpack area
• hi = there / in it

So A la motxilla no hi cap... literally feels a bit like:

• In the backpack, ... doesn’t fit in there

This may seem redundant to an English speaker, but it is very normal in Catalan. Catalan often uses this kind of clitic doubling, where the place is named and also repeated with hi.

Catalan often puts the place or context first if that is what the speaker wants to emphasize.

So:

• A la motxilla no hi cap la tovallola gran.

focuses first on the backpack.

A more English-like order would be:

• La tovallola gran no cap a la motxilla.

Both are understandable, but the original sentence highlights the location first: As for the backpack, the big towel doesn’t fit in it.

With cabre, Catalan very often uses the place as a complement introduced by a, especially when combined with hi.

So A la motxilla no hi cap... is a very natural Catalan way to say It doesn’t fit in the backpack.

For an English speaker, this can feel odd because English uses in, but Catalan does not always match English prepositions directly. In this kind of sentence, a + place plus hi is very common and idiomatic.

The subject is la tovallola gran.

You can tell because:

• cap is singular
• la tovallola gran is singular

So the meaning is:

• The big towel does not fit in the backpack.

Even though the subject comes after the verb, it is still the subject. Catalan word order is more flexible than English word order.

If the subject were plural, the verb would change:

• A la motxilla no hi caben les tovalloles grans.
• The big towels don’t fit in the backpack.

So cap matches la tovallola gran.

Because Catalan allows more flexible word order than English.

In English, we usually expect:

• The big towel doesn’t fit in the backpack.

But in Catalan, it is very natural to put the location first, then the verb, then the subject:

• A la motxilla no hi cap la tovallola gran.

This structure is especially common when the speaker is introducing the location as the main topic.

So the sentence is not unusual or poetic; it is normal Catalan word order.

In Catalan, adjectives often come after the noun.

So:

• la tovallola gran = the big towel

That is the normal order.

Also, with gran, position can affect nuance:

• una tovallola gran usually means a big towel (literal size)
• una gran tovallola could sound more like a great/impressive towel, depending on context

So in this sentence, tovallola gran clearly means the towel is physically large.

Because gran is the normal word for big/large in this context.

For a towel:

• tovallola gran = a large towel
• tovallola grossa would suggest something more like thick, bulky, or sometimes just unusually hefty

So if the point is that the towel is too large to fit, gran is the natural choice.

Yes. That is also grammatical and natural.

Compare the emphasis:

• A la motxilla no hi cap la tovallola gran.
  Focuses on the backpack first.

• La tovallola gran no cap a la motxilla.
  Focuses on the big towel first.

The basic meaning is the same. The difference is mostly about what comes first in the speaker’s mind or what they want to emphasize.

It is a very common pattern, yes.

You will often hear:

• No hi cap. = It doesn’t fit (in there).
• Hi cap? = Does it fit?
• No hi caben. = They don’t fit.

So once you know:

• cabre = to fit
• hi = there / in it

then no hi cap becomes a very useful everyday phrase.

The verb would have to agree with a plural subject.

Singular:

• A la motxilla no hi cap la tovallola gran.

Plural:

• A la motxilla no hi caben les tovalloles grans.

The change is:

• cap → singular
• caben → plural

That is a good way to confirm that la tovallola gran is the subject in the original sentence.