Si jo sabés la resposta, no copiaria del teu quadern.

It is a hypothetical conditional sentence.

The pattern is:

• Si + imperfect subjunctive = the condition
• conditional = the result

So:

• Si jo sabés la resposta = if I knew the answer
• no copiaria del teu quadern = I would not copy from your notebook

This is used for an unreal or unlikely situation in the present.

Because sabés is the imperfect subjunctive of saber.

Here, the speaker is not saying they actually know the answer. They are imagining a situation:

• sé = I know
• sabia = I knew / I used to know
• sabés = if I knew

After si in this kind of hypothetical sentence, Catalan uses the imperfect subjunctive:

• Si jo sabés la resposta...
• Si tingués temps...
• Si fos ric...

So sabés is the correct form for this unreal condition.

Copiaria is the conditional form of copiar.

It is used in the main clause to show what would happen under the imagined condition:

• Si jo sabés la resposta, no copiaria...

That matches English:

• If I knew..., I would not copy...

So the sentence follows the normal Catalan pattern for present unreal conditionals:

• si + imperfect subjunctive
• conditional

Yes, it could be left out.

Catalan often omits subject pronouns because the verb form usually makes the subject clear. So both are possible:

• Si jo sabés la resposta, no copiaria del teu quadern.
• Si sabés la resposta, no copiaria del teu quadern.

Including jo adds emphasis, as if the speaker is stressing I.

Because si without an accent means if.

• si = if
• sí = yes

So here it must be si, since the sentence is conditional.

Because saber is used for knowing facts, information, answers, or how to do something.

• saber la resposta = to know the answer
• saber nadar = to know how to swim

By contrast, conèixer is used for being familiar with people, places, or things:

• conec la Maria
• coneixem Barcelona

So la resposta goes with saber, not conèixer.

Because resposta is a feminine singular noun, so it takes the feminine singular article la.

• la resposta
• la pregunta
• la lliçó

It corresponds to the answer in English.

It means from your notebook.

Here:

• de = from / of
• el = the
• del = contraction of de + el

So:

• del teu quadern = from your notebook

With copiar, Catalan often uses copiar de to mean copy from someone or something.

Because Catalan normally contracts de + el into del.

So:

• de + el quadern → del quadern

This is very common in Catalan, just like:

• a + el → al
• de + els → dels

Teu means your when speaking to one person informally.

It agrees with quadern, which is masculine singular:

• el teu quadern = your notebook

Compare:

• la teva resposta = your answer
• els teus llibres = your books
• les teves notes = your notes

So teu changes form to match the noun it goes with.

Usually, yes.

In a school context, copiar d’algú or copiar del quadern d’algú often means copying someone else’s work, so it can imply cheating.

In this sentence, that is very likely the idea:
if I knew the answer myself, I would not need to copy from your notebook.

Because in Catalan, the normal negative particle no goes before the conjugated verb:

• no copiaria
• no sé
• no vull
• no vindrà

So no copiaria simply means I would not copy.

It is standard and natural to use a comma here.

The sentence begins with the si-clause, and the comma separates it from the main clause:

• Si jo sabés la resposta, no copiaria del teu quadern.

This is similar to English punctuation in sentences like:

• If I knew the answer, I wouldn’t copy.

Because in Catalan, many verb forms are the same for first person singular and third person singular in certain tenses and moods.

So sabés can mean:

• if I knew
• if he/she knew

Context or an explicit subject pronoun tells you which one is meant.

Here, jo makes it clear that it means I.

The accent mark shows that the stress falls on the last syllable:

• sa-BÉS

Without the accent, the word would not follow normal Catalan stress expectations.

So the accent helps show both pronunciation and, in many cases, the correct verbal form.

Then Catalan would use a past counterfactual pattern:

• Si hagués sabut la resposta, no hauria copiat del teu quadern.

That means:

• If I had known the answer, I would not have copied from your notebook.

So compare:

• Si jo sabés..., no copiaria... = present unreal
• Si hagués sabut..., no hauria copiat... = past unreal