Mật mã có dãy số.

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

So Mật mã có dãy số can be understood from context as:

• the code has a number sequence
• a code has a number sequence
• the password contains digits

Vietnamese often leaves this kind of information unstated unless it is important to be specific. Context tells you whether it is a code, the code, or codes in general.

Here, có means to have or to contain.

So the structure is:

• Mật mã = the code / password
• có = has
• dãy số = a string/sequence of numbers

A very common Vietnamese pattern is:

X có Y = X has Y

For example:

• Nhà có vườn. = The house has a garden.
• Bài này có lỗi. = This text has mistakes.

Be aware that có can also mean there is/there are in other sentences, so context matters.

Dãy số literally means a sequence of numbers or a string of digits.

In this sentence, it suggests that the code includes digits arranged in order. Depending on context, it could refer to:

• a numeric sequence
• a string of numbers
• digits in the password/code

The word dãy often gives the idea of a connected series or row of things. So dãy số is more than just number in general; it is a set or run of numbers.

Because số by itself usually just means number or numbers, while dãy số specifically means a sequence/string of numbers.

Compare:

• số = number / numbers
• dãy số = number sequence / string of digits

So if the idea is that the password contains several digits together, dãy số is more precise.

Not exactly.

These words are related, but they are not always interchangeable:

• mật mã often means code, cipher, or sometimes passcode
• mật khẩu usually means password
• mã số often means code number, ID number, or numeric code

In everyday modern usage, if you mean a website or app password, mật khẩu is often the most natural choice. If you mean a coded string, secret code, or passcode, mật mã may fit better.

So this sentence is understandable, but the most natural choice depends on what kind of code/password is meant.

Vietnamese word order here is straightforward:

subject + verb + object

So:

• Mật mã = subject
• có = verb
• dãy số = object

This is very similar to English The code has a number sequence.

Vietnamese often follows a fairly direct word order in simple statements, which can feel familiar to English speakers.

Vietnamese nouns usually do not change form for singular or plural.

So số can mean:

• number
• numbers

The sentence does not need a special ending like English -s. The idea of plurality is often understood from context or from words like dãy, which already suggests multiple numbers in a sequence.

Not exactly in the usual sense, but it behaves somewhat like a unit word.

Vietnamese has many words that indicate a type, unit, or grouping of things. Dãy means something like row, line, series, or sequence. So dãy số is a lexical combination meaning sequence of numbers.

It is better to think of dãy số as a set phrase or noun phrase rather than a normal classifier structure like:

• một con mèo = one cat
• một cái bàn = one table

Here, dãy contributes real meaning: it tells you the numbers form a series.

Word by word, the tones are:

• mật = heavy/falling tone
• mã = dipping-rising tone
• có = rising tone
• dãy = dipping-rising tone
• số = rising tone

A rough pronunciation guide for English speakers is:

• mật ≈ mut, but with a short vowel and a stopped ending
• mã ≈ mah, with a broken dipping-rising tone
• có ≈ kaw / koh with a rising tone
• dãy ≈ zai / yay-like depending on dialect, with a dipping-rising tone
• số ≈ soh with a rising tone

Two important notes:

1. d in southern Vietnamese often sounds like English y, while in northern Vietnamese d sounds more like z.
2. Final -t in mật is unreleased, so it ends abruptly.

Yes, it is grammatical and understandable. It sounds like a simple descriptive sentence: the code contains a numeric sequence.

That said, in real-life contexts, Vietnamese speakers might choose slightly different wording depending on what they mean:

• Mật khẩu có dãy số. = The password has a string of numbers.
• Mật mã gồm các chữ số. = The code consists of digits.
• Mật mã có chứa số. = The code contains numbers.

So your sentence is fine, but there may be more natural alternatives depending on the exact situation.

Not in this sentence if you want to express has/contains.

Without có, the relationship between mật mã and dãy số would become unclear. Vietnamese often omits words that English requires, but here có is doing important grammatical work: it tells us that the code possesses or contains the number sequence.

So:

• Mật mã có dãy số. = correct
• Mật mã dãy số. = incomplete or unnatural in this meaning

Not necessarily.

Mật mã có dãy số means the code has a sequence of numbers. That suggests numbers are included, but it does not strictly say the whole code is only numeric.

If you wanted to say the code is made up only of numbers, Vietnamese might say something more explicit, such as:

• Mật mã chỉ gồm số. = The code consists only of numbers.
• Mật mã toàn là số. = The code is all numbers.

So your sentence suggests contains numbers, not automatically numbers only.