Learn Hardcore German: Ich möchte das Buch morgen zurückgeben. - I would like to return the book tomorrow.

German main clauses normally put the finite verb (the one that’s conjugated for person and tense) in second position.
Here, möchte is the finite verb, so it must stand in position 2:

Ich (subject, position 1)
möchte (finite verb, position 2)
das Buch (object)
morgen (time)
zurückgeben (infinitive verb at the end)

When you have a modal verb like möchte, the other verb (here zurückgeben) stays in the infinitive and goes to the end of the clause. That’s why you see two verbs and this particular order.

What exactly does möchte mean, and how is it different from mag, will, and werde?

möchte means would like and sounds polite or tentative: Ich möchte das Buch zurückgeben = I would like to return the book.
mag (from mögen) means to like in the sense of I like chocolate, I like you: Ich mag dieses Buch = I like this book. It’s not used for I would like to do something in the same way English does.
will (from wollen) means want with a stronger, more determined tone: Ich will das Buch zurückgeben = I want to return the book (more forceful than möchte).
werde ... zurückgeben is future: Ich werde das Buch morgen zurückgeben = I will return the book tomorrow (a neutral future statement, not especially polite or impolite).

So möchte is the standard, polite way to express a wish or intention.

Is möchte a special tense, like the conditional or future?

Grammatically, möchte is the Konjunktiv II (subjunctive II) form of mögen, but in modern German it’s used primarily as a modal verb meaning would like.
Functionally, it behaves a bit like the English conditional would like, but Germany doesn’t call it a separate tense; it’s a mood (subjunctive) used in a polite, softened way.

Conjugation in the present is:

ich möchte
du möchtest
er / sie / es möchte
wir möchten
ihr möchtet
sie / Sie möchten

Why is zurückgeben at the very end of the sentence?

With modal verbs (like können, müssen, möchten, wollen, etc.), German puts the modal verb in second position and the main verb in the infinitive at the end of the clause.

Pattern:
Subject – conjugated modal – (other stuff) – infinitive

So: Ich – möchte – das Buch – morgen – zurückgeben.
This is a very standard word order whenever you see a modal verb.

Is zurückgeben one word or two? And what happens to it in other sentences?

zurückgeben is written as one word in the infinitive. It is a separable prefix verb: zurück- is the prefix, geben is the base verb.

With a modal verb or in the infinitive, it stays together:
- Ich möchte das Buch zurückgeben.
When geben is the finite verb in a main clause, the prefix separates and goes to the end:
- Ich gebe das Buch morgen zurück.

In subordinate clauses, the finite verb and prefix come back together at the end:

…, weil ich das Buch morgen zurückgebe.

Can I also say Ich gebe das Buch morgen zurück? How is that different from Ich möchte das Buch morgen zurückgeben?

Yes, Ich gebe das Buch morgen zurück is perfectly correct.

Ich gebe das Buch morgen zurück.
Neutral present-tense statement about what you are (definitely) doing tomorrow. It’s like I’m returning the book tomorrow.
Ich möchte das Buch morgen zurückgeben.
Emphasizes your wish / intention politely: I would like to return the book tomorrow.

In many real-life contexts, both could talk about a plan, but möchte sounds more polite or tentative, while gebe ... zurück sounds more direct and matter-of-fact.

Why is it das Buch and not den Buch or dem Buch?

Buch is a neuter noun, so its nominative and accusative singular article is das.

In this sentence, das Buch is the direct object (accusative). For neuter nouns, the article in nominative and accusative is the same:

Nominative: das Buch (The book is new. – Das Buch ist neu.)
Accusative: das Buch (I read the book. – Ich lese das Buch.)

Forms of der-words in singular are (for reference):

Masculine: der (nom.), den (acc.), dem (dat.)
Neuter: das (nom.), das (acc.), dem (dat.)
Feminine: die (nom.), die (acc.), der (dat.)

So den Buch (masculine accusative) is wrong because Buch is not masculine.

Why is Buch capitalized, but morgen is not?

In German, all nouns are capitalized, regardless of where they appear in the sentence. Buch is a noun, so it must be capitalized: das Buch.

morgen here is an adverb meaning tomorrow, and adverbs are not capitalized.

There is also a noun der Morgen (the morning), which is capitalized:

Ich möchte das Buch am Morgen zurückgeben. (I would like to return the book in the morning.)

So: capital letters for nouns (like Buch, Morgen the noun), lower case for adverbs (like morgen = tomorrow).

Can I move morgen to a different place in the sentence? For example: Ich möchte morgen das Buch zurückgeben.

Yes, German word order is quite flexible for adverbs like morgen. Both of these are correct:

Ich möchte das Buch morgen zurückgeben.
Ich möchte morgen das Buch zurückgeben.

The difference is very small and mostly about emphasis and rhythm:

… das Buch morgen … slightly emphasizes the book, then adds when.
… morgen das Buch … slightly emphasizes tomorrow first.

Both are perfectly natural; learners can treat them as interchangeable in everyday use.

Could I also say Ich möchte das Buch morgen zurückbringen? What is the difference between zurückgeben and zurückbringen?

Yes, Ich möchte das Buch morgen zurückbringen is also correct.

zurückgeben = to give back: focus on the act of handing it back to someone or to an institution.
- Typical with libraries, shops, or people: das geliehene Buch zurückgeben = to return the borrowed book.
zurückbringen = to bring back: focus on transporting it back to the place or person.
- Emphasizes taking it from where you are to where it belongs again.

In many everyday contexts (like returning a library book), both verbs are used and understood; context usually makes both acceptable.

How would this sentence look in the past, for example I wanted to return the book the next day?

The most natural way is to switch from möchte to wollte (past of wollen), because möchte does not have a commonly used past tense in everyday speech:

Ich wollte das Buch am nächsten Tag zurückgeben.
= I wanted to return the book the next day.

If you absolutely need a past of möchte, you would usually rephrase instead of conjugating mögen in the subjunctive past. For learners, Ich wollte … is the best choice for I wanted to …

How does this sentence change in a subordinate clause with weil or dass?

In subordinate clauses, the finite verb goes to the end of the clause. With a modal plus infinitive, you get two verbs at the end forming a kind of verb bracket:

Main clause: Ich möchte das Buch morgen zurückgeben.
With weil (because):
- …, weil ich das Buch morgen zurückgeben möchte.
With dass (that):
- …, dass ich das Buch morgen zurückgeben möchte.

Pattern in the subordinate clause:
… weil / dass – subject – (objects/adverbs) – infinitive – modal.

How do I replace das Buch with a pronoun in this sentence?

Since Buch is neuter, the pronoun is es in the accusative:

Ich möchte es morgen zurückgeben. = I would like to return it tomorrow.

Notice the word order: pronoun objects like es usually come earlier in the middle of the sentence, before longer elements like morgen:

More natural: Ich möchte es morgen zurückgeben.
Less natural: Ich möchte morgen es zurückgeben. (grammatically possible but sounds awkward)

Are there any pronunciation points I should watch for in Ich möchte das Buch morgen zurückgeben?

Yes, a few important ones:

Ich, möchte: the ch here is the front [ç] sound (like in German ich), not like English k or sh.
Buch: the ch is the back sound (like a harsh kh), because it follows a back vowel u.
ö in möchte: round your lips and say something like the vowel in British bird or hurt, but with rounded lips.
Final consonants at the ends of words (like -ch, -g, -n) should be clearly audible; don’t swallow them.

Saying the sentence slowly as Ich – möchte – das – Buch – morgen – zurückgeben and then speeding up will help get the rhythm and sounds right.