Phần này rất nhỏ.

In Vietnamese, demonstratives like này (this) usually come after the noun, not before it.

So:

• phần này = this part
• literally: part this

This is a very common Vietnamese pattern:

• nhà này = this house
• người này = this person
• cuốn sách này = this book

So if you are translating word-for-word from English, the order will often feel reversed.

Vietnamese often leaves out the verb to be when describing something with an adjective.

So:

• Phần này rất nhỏ.
• literally: This part very small.

This is a normal complete sentence in Vietnamese.

You do not need là here. In fact, là would usually sound wrong in this kind of sentence.

A useful rule:

• noun + adjective = noun is adjective
• Phần này nhỏ. = This part is small.
• Phần này rất nhỏ. = This part is very small.

Phần can mean part, portion, section, or component, depending on context.

In this sentence, it most naturally means something like:

• this part
• this section
• this portion

For example, phần could refer to:

• part of a machine
• part of a text
• part of a body
• a portion of food
• a section in a test or document

So the exact English translation depends on the situation.

Rất means very and it goes before the adjective it modifies.

So:

• nhỏ = small
• rất nhỏ = very small

This is the normal pattern:

• rất đẹp = very beautiful
• rất nhanh = very fast
• rất khó = very difficult

So the structure is:

• subject + rất + adjective

In your sentence:

• Phần này = this part
• rất nhỏ = very small

Yes. That would simply mean This part is small instead of This part is very small.

Compare:

• Phần này nhỏ. = This part is small.
• Phần này rất nhỏ. = This part is very small.

So rất just adds emphasis.

Because nhỏ is the adjective describing the subject phần này.

Vietnamese often uses this pattern:

• subject + adjective
• Cái bàn lớn. = The table is big.
• Con mèo đen. = The cat is black.
• Phần này nhỏ. = This part is small.

In this sentence, nhỏ is acting as the main description of the subject, so it comes after the subject phrase.

Yes. Nhỏ often means small or little, depending on context.

Examples:

• một cái nhà nhỏ = a small house
• em nhỏ = small child / little child
• phần nhỏ = small part

In your sentence, small is the most natural translation.

Usually no, not when an adjective is directly describing the subject.

So:

• Phần này rất nhỏ. = correct
• Phần này là rất nhỏ. = incorrect

Là is more commonly used when linking one noun to another noun, or for identification/classification.

For example:

• Đây là giáo viên. = This is a teacher.
• Phần này là phần mở đầu. = This part is the introduction.

But with plain adjectives like nhỏ, đẹp, cao, khó, Vietnamese normally does not use là.

Sometimes, but not always.

Both nhỏ and bé can relate to small size, but nhỏ is the more general and neutral word for small.

• nhỏ = small, little
• bé = small, little, tiny; often sounds softer, cuter, or is used more with children, animals, and informal speech

For an object or section, nhỏ is usually the safer choice.

So:

• Phần này rất nhỏ. = very natural
• Phần này rất bé. = possible in some contexts, but less neutral

Yes. Này is a demonstrative, like this in English.

It points to something near the speaker, or something currently being discussed.

Examples:

• cuốn sách này = this book
• người này = this person
• phần này = this part

A common contrast is:

• này = this
• đó / kia = that

So:

• phần này = this part
• phần đó = that part

A learner-friendly guide:

• Phần: roughly like fuhn, with a falling tone
• này: roughly like nye, also with a falling tone
• rất: short, something like zut or ruht, with a rising tone
• nhỏ: roughly like nyaw, with a dipping/asking tone

A few pronunciation notes:

• ph is pronounced like f
• nh is like the ny sound in canyon or onion
• r changes by dialect:
  • in the North, it is often a strong z/zh-like sound
  • in the South, it may sound more like r or y depending on speaker
• t at the end of rất is unreleased, so it ends very abruptly

The tones are important:

• phần = huyền tone
• này = huyền tone
• rất = sắc tone
• nhỏ = hỏi tone

No, not here.

Phần is already a noun meaning part/section/portion, so you can directly say:

• phần này = this part

You do not need cái in this sentence.

Vietnamese classifiers are common, but they are not used with every noun in every situation, and many nouns like phần can stand on their own naturally.

It is neutral and completely natural.

Phần này rất nhỏ. could be used in many contexts, such as:

• explaining a diagram
• describing an object
• talking about a document or exam
• discussing a portion of food or material

It is not especially formal or especially slangy. It is standard everyday Vietnamese.

Yes, depending on context.

Although nhỏ often refers to physical size, it can also describe something abstract, such as:

• a small section of a document
• a minor part of a problem
• a small amount or contribution

So Phần này rất nhỏ could mean:

• this part is physically tiny
• this section is short
• this portion is minor

The context tells you exactly which meaning is intended.