Passive voice?

He gave me the book which is written by XY. I believe it's passive.

I think that it is an adj and not a passive voice form, cuz the passive voice should be followed by the auxilary " to be " in a mentionned tense !

Yes, written is the Passive Voice here. He gave me the book written by XY is the shortened form of He gave me the book which was written by XY. Another way to say it is: He gave me the book by XY.
If i were you, I would choose a rather than the here:
He gave me a book written by XY.
He gave me a book by XY.
GN

Thank you both for your answers.

Gigilian Nguye, I was thinking in the same way, but if we drop "to be", does it mean that we are still talking about the Passive Voice? Maybe it's a particle?

Yes, it was "a" in the original setence

He gave me the book that was written by XY. Non-restrictive clauses use WHICH and they can be left out of the sentence without changing the meaning. eg: 'He gave me the book, which I placed on the table.' THAT is needed here because 'that was written by XY' helps create the total meaning of the sentence, it's essential. Thanks

Hi,
It's still the same meaning when you add to be: He gave me a book which was written by XY.
It will just sound more formal.
Is that what you mean?

What is then the difference between the Passive Voice and the participle?

My English book reads:

We often use participles to add extra information to the idea in the sentence. The past participle sometimes (-ed forms) acts as an adjective. The present participle (-ing forms) sometimes gives background information.

Returned now to national prominence, Groucho embar

be + past participle = passive voice
And there are some other uses that are different between them: Past Perfect + past participle, Present Perfect + past participle, something must be done (passive voice),...
GN

Thank you

I've added some information to my previous post.

That is very nice, thank you too.
GN