Ngày mai, tôi sẽ đặt phòng ở khách sạn.

The sentence follows a very common Vietnamese pattern:

• Ngày mai = tomorrow
• tôi = I
• sẽ = will
• đặt phòng = book a room / make a room reservation
• ở khách sạn = at a hotel / in a hotel

So the structure is:

• time expression + subject + future marker + verb phrase + location

A very literal gloss would be:

• Tomorrow, I will book room at hotel.

Vietnamese often leaves out words like a and the, which English requires.

Putting ngày mai at the front sets the time first. This is extremely natural in Vietnamese.

It is similar to saying in English:

• Tomorrow, I will book a hotel room.

Vietnamese often places time expressions near the beginning of the sentence, especially when the speaker wants to frame the whole statement in time.

You could also hear time expressions in other positions, but sentence-initial placement is very common and very natural.

Tôi means I, but it is a neutral and somewhat formal pronoun.

It is safe to use in many situations, especially when you are learning. However, in real conversation, Vietnamese often uses different pronouns depending on:

• age
• relationship
• social context
• level of politeness

For example, instead of tôi, someone might say:

• mình
• em
• anh
• chị
• con
• cháu

So tôi is correct, but it is not the only way to say I.

Sẽ is a future marker. It shows that the action has not happened yet and is expected to happen in the future.

In this sentence:

• tôi sẽ đặt phòng = I will book a room

Vietnamese does not conjugate verbs the way English does. The verb đặt does not change form. Instead, words like sẽ help show time.

So:

• đặt = book / reserve
• sẽ đặt = will book

No, not always.

Vietnamese often relies on time words such as ngày mai to show that something is in the future. Because of that, sẽ can sometimes be omitted if the future meaning is already clear.

For example:

• Ngày mai, tôi đặt phòng ở khách sạn.

This can still mean Tomorrow, I’m booking a hotel room or Tomorrow, I will book a hotel room, depending on context.

Adding sẽ makes the future meaning more explicit. So in learner Vietnamese, using sẽ is often a good idea when you want to be clear.

Đặt phòng means to book a room or to reserve a room.

• đặt = to reserve / to place / to book
• phòng = room

Together, đặt phòng is a very common phrase used for:

• hotel rooms
• meeting rooms
• sometimes other kinds of room reservations depending on context

Also, đặt is used in many other booking situations:

• đặt bàn = reserve a table
• đặt vé = book a ticket
• đặt chỗ = reserve a place/seat

Vietnamese often leaves out một (one / a) when the meaning is already clear.

So:

• đặt phòng = book a room / book rooms / make a room reservation

In English, you usually need a room or the room, but Vietnamese does not require an article in the same way.

You can say:

• đặt một phòng = book one room / book a room

Adding một makes the number more explicit. Without it, the phrase is still perfectly natural.

Here, ở khách sạn means something like at a hotel or in a hotel.

The word ở often marks location. It is very common and flexible, and can often be translated as:

• at
• in
• staying/living at

In this sentence, it helps specify where the room is being booked:

• đặt phòng ở khách sạn = book a room at a hotel

Depending on context, Vietnamese speakers might also use slightly different phrasing, such as:

• đặt phòng khách sạn

That is also very common and often sounds more like book a hotel room.

Vietnamese does not have articles that work like English a, an, and the.

So:

• khách sạn can mean a hotel, the hotel, or just hotel in a general sense

The exact meaning depends on context.

That is why English speakers often feel something is missing, but for Vietnamese, the sentence is complete and natural.

Sometimes, yes.

Vietnamese often omits subjects when they are obvious from context. For example, in conversation, if it is already clear that I am the one speaking about my own plan, a speaker may leave out tôi.

But for a full, clear sentence—especially in textbook Vietnamese—keeping tôi is normal and helpful.

So:

• Ngày mai, tôi sẽ đặt phòng ở khách sạn. = full and clear
• Ngày mai sẽ đặt phòng ở khách sạn. = possible in context, but less explicit

Tone is very important in Vietnamese, and several words here have marked tones:

• Ngày — has a falling tone mark
• sẽ — has the ngã tone mark
• đặt — has a heavy, low, stopped tone
• ở — has the hook-above tone
• sạn — also has a heavy tone

A few pronunciation notes:

• ngày mai: the ng sound is like the end of English sing, but at the beginning of the word
• tôi: roughly like toy, but not exactly
• đ in đặt is a distinct Vietnamese d-like sound; it is not the same as plain d
• ph in phòng sounds like f
• kh in khách is a breathy consonant, somewhat like the ch in German Bach or Scottish loch

If you want to sound natural, learning the tones is just as important as learning the vocabulary.

Yes, it is natural and correct.

That said, depending on what exactly you mean, Vietnamese speakers might also say:

• Ngày mai, tôi sẽ đặt phòng khách sạn.
• Ngày mai, tôi sẽ đặt một phòng ở khách sạn.

These are slightly different in nuance:

• đặt phòng ở khách sạn emphasizes booking a room at a hotel
• đặt phòng khách sạn is a very common compact way to say book a hotel room
• đặt một phòng makes the number one room clearer

So the original sentence is good, but Vietnamese offers several natural variations.