Si avui no tinguessis deures, vindries al cinema amb mi?

Because this sentence is talking about a hypothetical or unreal situation in the present: If you didn’t have homework today, would you come to the cinema with me?

In Catalan, for this kind of if-clause, you normally use:

• si + imperfect subjunctive
• and then conditional in the main clause

So:

• Si avui no tinguessis deures = If you didn’t have homework today
• vindries al cinema amb mi? = would you come to the cinema with me?

This is very similar to the English second conditional.

Tinguessis is the imperfect subjunctive form of the verb tenir (to have), for tu.

So the breakdown is:

• tenir = to have
• tingués / tinguessis / tingués... = imperfect subjunctive forms

Here, tinguessis means something like you had in a hypothetical sense, not a simple factual past.

Vindries is the conditional form of venir (to come), for tu.

• venir = to come
• vindries = you would come

In Catalan, the normal pattern for this kind of sentence is:

• Si + imperfect subjunctive
• conditional

So:

• Si... tinguessis...
• ... vindries...?

This matches English If..., would you...?

Yes, very close.

English:

• If you didn’t have homework today, would you come to the cinema with me?

Catalan:

• Si avui no tinguessis deures, vindries al cinema amb mi?

A useful comparison is:

• English: if + past form, would + verb
• Catalan: si + imperfect subjunctive, conditional

So the overall meaning and use are very similar, even though the grammar labels are a bit different.

Here deures means homework.

In Catalan, deures is often used in the plural when talking about school homework:

• Tinc deures = I have homework
• No tinc deures = I don’t have homework

It can also mean duties in other contexts, but in this sentence the natural meaning is clearly homework.

Because al is the contraction of:

• a + el = al

So:

• al cinema = to the cinema

This kind of contraction is very common in Catalan. For example:

• a + el → al
• de + el → del

So vindries al cinema literally means would you come to the cinema.

Because after a preposition like amb (with), Catalan uses the stressed pronoun, not the subject pronoun.

So:

• jo = I
• mi = me

That is why you say:

• amb mi = with me

not:

• amb jo

This works much like English with me, not with I.

Yes. Avui (today) is fairly flexible in Catalan.

The original sentence is:

• Si avui no tinguessis deures, vindries al cinema amb mi?

You could also hear:

• Si no tinguessis deures avui, vindries al cinema amb mi?

Both are natural. Putting avui earlier often gives it a little more emphasis, but the meaning stays basically the same.

Yes, tenir is an irregular verb, so its subjunctive stem changes.

You can think of it like this:

• infinitive: tenir
• subjunctive stem: tingu-

Then the imperfect subjunctive ending is added:

• tinguessis

Many very common Catalan verbs are irregular in the subjunctive, so this is something learners just have to get used to. Since tenir is used all the time, this form is worth memorizing.

Yes, depending on perspective.

• vindries al cinema amb mi? = would you come to the cinema with me?
• aniries al cinema amb mi? = would you go to the cinema with me?

Both can be natural. The choice depends on how the speaker imagines the movement:

• venir often reflects movement toward the speaker’s perspective
• anar means to go

In many real conversations, either could work.

Grammatically, no directly negates the verb tinguessis:

• no tinguessis deures = you didn’t have homework

So the condition is specifically if you did not have homework today.

Without no, the meaning would reverse:

• Si avui tinguessis deures... = If you had homework today...

The sentence as written is already perfectly natural and common in speech.

In informal conversation, pronunciation may be reduced a bit, but grammatically it would usually stay the same:

• Si avui no tinguessis deures, vindries al cinema amb mi?

A speaker might also choose slightly different wording, such as:

• Si avui no tinguessis deures, vindries amb mi al cinema?

That version is also natural. The difference is mainly word order, not meaning.