Đây là lệnh mới.

Đây means this or here, depending on context. In Đây là lệnh mới, it works like this in This is a new command.

A very common pattern in Vietnamese is:

Đây là ... = This is ...

So:

• Đây là sách. = This is a book.
• Đây là lệnh mới. = This is a new command.

Là is the word used to link two nouns or noun phrases, similar to is / am / are in English in sentences like This is... or That is...

So the structure is:

Đây + là + lệnh mới
This + is + a new command

However, Vietnamese does not always use là the way English uses to be. It is especially common when identifying or defining something.

For this sentence, là is completely natural and expected.

In Vietnamese, adjectives usually come after the noun they describe.

So:

• lệnh mới = new command
• literally: command new

More examples:

• sách mới = new book
• xe mới = new car
• ý tưởng mới = new idea

This is one of the most important word-order differences from English.

It can mean any of those, depending on context.

Lệnh often refers to:

• a command
• an order
• an instruction
• sometimes even a system command, if the context is technical

So the exact English translation depends on the situation:

• military/government context: order or command
• software/computing context: command
• general directive context: instruction or order

Vietnamese does not use articles like a, an, and the the same way English does.

So lệnh mới can mean:

• a new command
• the new command

The exact meaning depends on context.

If you want to make a new command more explicit, you could say:

Đây là một lệnh mới.

Here, một literally means one, but it can also function like a/an in many contexts.

Yes, absolutely.

Both are correct:

• Đây là lệnh mới.
• Đây là một lệnh mới.

The version with một can sound a little more explicit, like This is a new command or This is one new command depending on context.

The version without một is also very natural and common. Vietnamese often leaves out words that English would require.

Not exactly.

Both relate to this, but they are used differently.

• đây often stands alone and can mean this / here
• này usually comes after a noun to mean this

Compare:

• Đây là lệnh mới. = This is a new command.
• lệnh này = this command

So:

• Đây là lệnh mới. = talking about something: This is a new command.
• Lệnh này mới. = This command is new.

That is an important difference.

A rough guide:

• Đây: sounds somewhat like day, but with the Vietnamese vowel sound and the đ sound, which is like English d
• là: similar to lah, with a low falling tone
• lệnh: starts with l, then a short vowel, and ends with nh; the tone is heavy and clipped
• mới: somewhat like muh-ee blended together, with a rising tone

The tones matter a lot:

• đây has the ngang tone (level)
• là has the huyền tone (falling)
• lệnh has the nặng tone (heavy, low, cut short)
• mới has the sắc tone (rising)

If your tones are wrong, people may still understand from context, but correct tones make a big difference.

The structure is:

Đây + là + noun phrase

More specifically:

• Đây = this
• là = linking verb, like is
• lệnh mới = noun + adjective = new command

So the whole pattern is:

This is + noun phrase

You can reuse it easily:

• Đây là nhà tôi. = This is my house.
• Đây là bạn tôi. = This is my friend.
• Đây là vấn đề mới. = This is a new problem.

Yes. Lệnh often sounds more formal, official, or technical than a very casual everyday noun.

For example, it may be used in:

• military or official contexts
• workplace instructions
• computing or programming
• command-based systems

So Đây là lệnh mới could sound like:

• This is the new order
• This is a new instruction
• This is the new command

The context tells you how formal or technical it is.