zhè shì wéiyī de wèntí.

In this sentence, 这 means this as a standalone pronoun: This is the only problem.

So:

• 这 = this / this thing
• 这个 can also sometimes be used similarly in speech, but 这 is perfectly natural here.

Compare:

• 这是唯一的问题。 = This is the only problem.
• 这个是唯一的问题。 = also possible in conversation, but often sounds a little more pointed or colloquial

If you wanted to say this problem is the only problem, that would be a different structure, such as:

• 这个问题是唯一的问题。

是 is the verb to be in this kind of sentence. It links 这 and 唯一的问题.

So the structure is:

• 这 = this
• 是 = is
• 唯一的问题 = the only problem

Altogether:

• 这是唯一的问题。
• This is the only problem.

This is a standard A 是 B pattern in Mandarin.

的 is used here to connect a modifier to a noun.

• 唯一 = only / sole
• 问题 = problem / question
• 唯一的问题 = the only problem

So 唯一 modifies 问题, and 的 links them.

This is very common in Mandarin:

• 重要的问题 = an important problem
• 简单的问题 = a simple question
• 唯一的问题 = the only problem

Without 的, 唯一问题 would usually sound unnatural in normal speech here.

唯一 means only, sole, or one and only.

In this sentence, it means there is just one problem:

• 唯一的问题 = the only problem

Be careful: 唯一 usually means the only one, not unique in the sense of special or unusual. For unique in that sense, Mandarin often uses words like 独特.

So:

• 唯一的问题 = the only problem
• 独特的问题 = a unique/distinctive problem

It can mean either problem or question, depending on context.

• 问题 = question
• 问题 = problem / issue

In 这是唯一的问题。, it often means This is the only problem or This is the only issue.

If the context were about asking things in class, it could mean This is the only question. Context decides which meaning is intended.

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

So 唯一的问题 naturally means the only problem without needing a separate word for the.

The idea of definiteness is often understood from context or from the wording itself. Since 唯一 means only, it already makes the noun definite in meaning.

In standard Mandarin, 这是唯一的问题 is the natural form.

• 唯一的问题 = correct and natural
• 唯一问题 = usually sounds incomplete or unnatural here

That is because 唯一 is modifying 问题, and in this kind of modifier + noun phrase, 的 is normally needed.

It is actually quite close to English here.

English:

• This is the only problem.

Mandarin:

• 这 是 唯一 的 问题。
• This is only + linking particle + problem.

The main difference is inside 唯一的问题, where Mandarin uses 的 to connect the modifier and the noun.

So the overall structure is very straightforward for English speakers.

No. 这 by itself means this.

If you want these, you would usually say:

• 这些 = these

So:

• 这是唯一的问题。 = This is the only problem.
• 这些是唯一的问题。 = These are the only problems.
  This sentence is grammatically possible, though the meaning would depend on context.

The pinyin is:

• zhè shì wéiyī de wèntí

A few pronunciation notes:

• 这 zhè = 4th tone
• 是 shì = 4th tone
• 唯 wéi = 2nd tone
• 一 yī = usually written 1st tone here
• 的 de = neutral tone
• 问 wèn = 4th tone
• 题 tí = 2nd tone

Natural rhythm:

• 这 / 是 / 唯一的 / 问题

Try not to stress every syllable equally. 的 is light and unstressed.

Yes. If you want to emphasize that this is the one and only problem, you can say:

• 这就是唯一的问题。

Here, 就 adds emphasis, something like:

• This is exactly the only problem
• This is the one thing that's the only problem

It makes the statement sound stronger or more pointed.

Yes. 这个是唯一的问题。 would be understood.

However, there is a slight difference in feel:

• 这是唯一的问题。 = smoother, standard, concise
• 这个是唯一的问题。 = more conversational or slightly more emphatic, like this one is the only problem

Both are possible, but 这是唯一的问题。 is the cleanest version.

It is a full sentence.

Breakdown:

• 这 = subject
• 是 = verb
• 唯一的问题 = predicate noun phrase

So this is not just a vocabulary chunk. It is a complete statement meaning:

• This is the only problem.

Inside it, 唯一的问题 is a noun phrase, but the whole thing is a sentence.