Biển rất xanh.

Vietnamese often does not use a verb like to be in simple descriptions.

So:

• Biển = sea
• rất = very
• xanh = blue/green

Putting them together gives Biển rất xanh = The sea is very blue.

This is very normal in Vietnamese. Adjectives can function directly as the predicate, so you do not need a separate word for is here.

Biển means sea or ocean, depending on context.

In a sentence like Biển rất xanh, it usually means the sea in a general sense, not necessarily one specific sea by name.

A few related words:

• biển = sea
• đại dương = ocean
• bờ biển = coast / seaside
• bãi biển = beach

So be careful: biển is not beach.
If you want The beach is very beautiful, you would usually say something with bãi biển, not just biển.

Rất is an adverb meaning very.

It goes before the adjective:

• xanh = blue/green
• rất xanh = very blue/green

This is the normal word order in Vietnamese:

• noun + adverb + adjective

So:

• Biển xanh = The sea is blue.
• Biển rất xanh = The sea is very blue.

Other examples:

• Trời rất đẹp = The sky/weather is very beautiful.
• Cô ấy rất cao = She is very tall.

This is a very common question. Xanh can cover both blue and green, especially in basic usage.

Context usually tells you which one is meant.

In Biển rất xanh, xanh is understood as blue, because the sea is typically described as blue.

Vietnamese can also be more specific:

• xanh dương = blue
• xanh da trời = sky blue
• xanh lá cây = green

So:

• Biển rất xanh naturally means The sea is very blue
• Lá cây rất xanh naturally means The leaves are very green

The base word xanh is flexible, and context does a lot of the work.

No, that word order is not natural.

The normal order is:

• Biển
  • rất
    • xanh

That is because rất modifies the adjective xanh, so it comes before it.

Correct:

• Biển rất xanh

Not natural:

• Biển xanh rất

A useful pattern to remember is:

• Noun + degree word + adjective

For example:

• Nước rất lạnh = The water is very cold.
• Con đường rất dài = The road is very long.

Yes. Biển xanh is perfectly natural.

It simply means:

• The sea is blue
• or sometimes blue sea, depending on context

Vietnamese often allows short adjective phrases like this.

Compare:

• Biển xanh = The sea is blue / blue sea
• Biển rất xanh = The sea is very blue

Adding rất just strengthens the description.

Yes. Vietnamese does not have articles like a, an, and the in the same way English does.

So biển can mean:

• sea
• the sea
• a sea

The exact meaning depends on context.

In a simple descriptive sentence like Biển rất xanh, English usually translates it as The sea is very blue or Sea water is very blue, depending on the situation. Most naturally, though, English uses the sea.

This is normal in Vietnamese: nouns often appear without an article.

A rough pronunciation guide is:

• Biển ≈ bee-ən or bee-ehn with a rising-breaking tone
• rất ≈ in the North, something like zut; in the South, often closer to yut
• xanh ≈ roughly sanh or syanh, depending on accent

A few pronunciation notes:

• r changes a lot by region:
  • Northern Vietnamese: often like z
  • Southern Vietnamese: often like y or a soft r
• x is like an s sound, not like English x
• nh is a single consonant sound, somewhat like the ny in canyon

If you are learning tones, Biển rất xanh has important tone patterns, so it is best to hear it from a native speaker or audio source rather than rely only on English spelling.

It probably is just because it appears at the beginning of the sentence.

Vietnamese capitalization works much like English in that respect:

• At the start of a sentence: Biển rất xanh.
• In the middle of a sentence: Hôm nay biển rất xanh.

So the word itself is not inherently capitalized.

Grammatically, xanh could refer to either blue or green, but in normal usage this sentence is understood as The sea is very blue.

Why?

Because meaning is guided by context and common expectations:

• sea is commonly described as blue
• leaves/grass are commonly described as green

So although the word xanh is broad, the whole sentence strongly suggests blue, not green.

If someone wanted to make green especially clear in another context, they might use a fuller phrase such as xanh lá cây.

Not in this sentence pattern.

If you want a full sentence meaning The sea is very blue, the normal structure is:

• Biển rất xanh

If you want to use xanh before a noun, Vietnamese usually needs a different structure, and it is not as simple as directly copying English adjective placement.

For example:

• biển xanh can mean blue sea
• but xanh biển is not the normal way to say that

So for learners, it is safest to remember:

• descriptive sentence: Biển rất xanh
• noun phrase: biển xanh

Yes, it is natural and simple.

It sounds like a basic observation, similar to saying:

• The sea is very blue.

It is the kind of sentence you might say when looking at the sea, especially on a clear day.

If you wanted to sound a little more expressive, you could also say things like:

• Biển hôm nay rất xanh. = The sea is very blue today.
• Nước biển rất xanh. = The sea water is very blue.
• Biển xanh quá! = The sea is so blue!

But Biển rất xanh by itself is completely normal.

Both are natural, but they focus slightly differently.

• Biển rất xanh = The sea is very blue.
• Nước biển rất xanh = The seawater is very blue.

Biển talks about the sea as a whole.
Nước biển focuses more specifically on the water.

In many situations, the difference is small, but nước biển can feel a bit more concrete or descriptive.

For example:

• Looking at a landscape: Biển rất xanh.
• Talking about the color of the water itself: Nước biển rất xanh.