Chiếc váy này rất vừa vặn.

Chiếc is a classifier. Vietnamese often uses classifiers before nouns, especially when talking about a specific object.

In chiếc váy này:

• chiếc = classifier for certain individual objects
• váy = dress
• này = this

So chiếc váy này means this dress.

For clothing, classifiers are sometimes included for a more natural or complete noun phrase, especially in careful speech. In everyday conversation, people may also leave the classifier out and just say váy này.

Yes, absolutely.

Both are natural:

• Chiếc váy này rất vừa vặn.
• Váy này rất vừa vặn.

Using chiếc can sound a little more specific, descriptive, or polished. Leaving it out is very common in everyday speech.

So for a learner:

• with classifier = slightly fuller, more explicit
• without classifier = still correct and very natural

Because Vietnamese demonstratives usually come after the noun, not before it like in English.

Compare:

• English: this dress
• Vietnamese: váy này / chiếc váy này

So the order is:

• noun phrase + này = this ...
• noun phrase + đó / kia = that ...

This is a very common pattern in Vietnamese.

Rất means very. It goes before an adjective.

So:

• vừa vặn = well-fitting / fitting properly
• rất vừa vặn = very well-fitting

This is a standard Vietnamese pattern:

• rất đẹp = very beautiful
• rất nhỏ = very small
• rất vừa vặn = very well-fitting

Vừa vặn means something like:

• fits well
• is the right size
• is nicely fitted
• is neither too tight nor too loose

It is especially common for clothes, shoes, or anything that needs to fit the body properly.

So with váy, rất vừa vặn means the dress fits very well.

Not exactly.

Vừa by itself can mean several things depending on context, such as:

• just enough
• suitable
• to fit
• just now (in other contexts)

With clothing, vừa can already mean fit:

• Chiếc váy này vừa. = This dress fits.

But vừa vặn sounds more clearly like fits properly / fits nicely / fits just right. It often feels a bit more descriptive and natural when talking about fit.

So:

• vừa = fits
• vừa vặn = fits well, fits just right

It is written as two separate written syllables in Vietnamese: vừa vặn.

That is normal in Vietnamese. Many compounds or fixed expressions are written with spaces between syllables.

So even though it functions like one adjective in meaning, it is still written as:

• vừa vặn

not as a single combined English-style word.

The sentence follows this pattern:

• classifier + noun + demonstrative + degree word + adjective

Breaking it down:

• chiếc = classifier
• váy = dress
• này = this
• rất = very
• vừa vặn = well-fitting / the right size

So literally, the structure is close to:

• this dress very well-fitting

That is normal Vietnamese word order.

Vietnamese often does not need a verb equivalent to English to be when describing something with an adjective.

So:

• Chiếc váy này rất vừa vặn.

does not need a separate word for is.

English needs:

• This dress is very well-fitting.

Vietnamese can simply put the adjective after the noun phrase.

This is a very important Vietnamese pattern:

• Cô ấy đẹp. = She is beautiful.
• Trời nóng. = The weather is hot.
• Chiếc váy này rất vừa vặn. = This dress is very well-fitting.

A very common way is to use có ... không around the adjective:

• Chiếc váy này có vừa vặn không?
• Váy này có vừa không?

This means:

• Does this dress fit well?
• Does this dress fit?

You could also ask more naturally in conversation:

• Chiếc váy này vừa vặn chứ?

That sounds like This dress fits well, right?

A rough pronunciation guide is:

• Chiếc ≈ chiếc with a high, sharp tone
• váy ≈ like vye with a rising tone
• này ≈ like nye with a level-ish falling tone depending on dialect
• rất ≈ short, clipped, with a sharp tone
• vừa ≈ roughly vuh-uh with a falling tone on the first syllable
• vặn ≈ roughly vun with a heavy low tone and glottal stop

A rough English-friendly approximation of the whole sentence might be:

chee-ek vay nyee zut vuh-uh vun

But that is only approximate. The tones are very important in Vietnamese, so listening to native audio is much better than relying on English spelling.

Yes, it sounds natural.

A native speaker might say it when:

• trying on clothes
• commenting on how a dress fits someone
• shopping
• giving an opinion about size and fit

Depending on context, people might also say:

• Chiếc váy này vừa lắm. = This dress fits very well.
• Váy này rất vừa. = This dress fits very well.
• Chiếc váy này mặc rất vừa vặn. = This dress wears/fits very well.

So your original sentence is natural and useful.