Vòi nước ở trong bếp.

Vòi nước means faucet, tap, or water tap.

Literally:

• vòi = spout, nozzle, trunk, tap
• nước = water

So vòi nước is specifically a water faucet/tap, not just any kind of nozzle.

Ở is commonly used to talk about location.

In this sentence, it works like is located at/in.

So the structure is:

• Vòi nước = the faucet
• ở trong bếp = is in the kitchen

A very literal breakdown would be:

• The faucet
  • is located
    • inside the kitchen

Vietnamese often uses ở where English would use is in / is at / is located in.

Good question. They do different jobs.

• ở marks location: is at/in
• trong means inside

So ở trong bếp means is inside the kitchen.

If you say just ở bếp, it can sound less natural in many situations, and it does not express inside as clearly.
Ở trong bếp is a very common and natural way to say in the kitchen.

You can think of it like this:

• ở = tells you something has a location
• trong bếp = names that location more specifically

It can mean either, depending on context.

Common meanings of bếp:

• stove
• kitchen
• cooking area

In trong bếp, it normally means in the kitchen.

If someone were talking about the appliance itself, context would make that clear.

The word order is:

• Vòi nước = subject
• ở trong bếp = location

So the pattern is:

thing/person + ở + location

That is very common in Vietnamese.

A word-for-word style gloss would be:

faucet + located at/inside + kitchen

Vietnamese does not need to match English word order exactly to express the same idea.

Vietnamese does not usually use articles like a, an, or the the way English does.

So vòi nước can mean:

• a faucet
• the faucet

The exact meaning depends on context.

If the meaning shown to the learner is The faucet is in the kitchen, that is perfectly normal. Vietnamese often leaves definiteness unstated unless it needs to be emphasized.

Yes, you could, but it changes the feel slightly.

Cái is a common classifier for objects.
So cái vòi nước means something like the faucet or that faucet as a concrete object.

Compare:

• Vòi nước ở trong bếp. = neutral, simple statement
• Cái vòi nước ở trong bếp. = more explicit/object-focused, often used in speech

In many simple sentences, the classifier is optional unless you are:

• counting something
• pointing something out
• contrasting it with something else
• making the noun phrase sound more specific in conversation

You can say vòi, but vòi nước is clearer.

That is because vòi by itself can refer to several kinds of spouts or nozzle-like things, not only a faucet. For example, it can also mean:

• a hose nozzle
• a spout
• an elephant’s trunk

So if you mean a household faucet/tap, vòi nước is the safest and most natural choice.

Yes. It is a complete and natural Vietnamese sentence.

Vietnamese does not always need a separate verb exactly like English to be in every sentence. In location sentences, ở often does the job of expressing where something is.

So even without an English-style is,
Vòi nước ở trong bếp is fully grammatical and complete.

A rough guide is:

• vòi — rising-falling tone pattern in Southern speech / low falling in Northern; sounds roughly like voy
• nước — starts like nư- with a short, clipped tone
• ở — like a short uh sound with a rising/broken quality depending on accent
• trong — roughly chawng or tchong depending on accent
• bếp — roughly byep with a sharp rising tone

A very rough English-friendly approximation: voy nyuhk uh chong byep

But tone and vowel quality matter a lot, so approximations only help a little. If you want, I can also break it down by Northern and Southern pronunciation.