zhè shì xǐyīfěn.

这 means this. It points to something near the speaker.

In 这是洗衣粉, 这 is the subject of the sentence, so the structure is:

这 + 是 + 洗衣粉
this + is + laundry detergent

So the whole sentence literally follows the same basic pattern as English: This is laundry detergent.

是 means to be in the sense of is / am / are when connecting one noun to another noun.

In this sentence, it links:

• 这 = this
• 洗衣粉 = laundry detergent

So 这是洗衣粉 means This is laundry detergent.

A useful thing to remember: 是 is commonly used when one thing is being identified as another thing.

Both can be correct, but they are used a little differently.

• 这 = this
• 这个 = this one / this thing

In 这是洗衣粉, 这 is being used by itself as a pronoun, so 这 is natural.

You could also say:

• 这个是洗衣粉。

That also means This is laundry detergent, but it sounds a bit more like This one is laundry detergent.

So:

• 这 = very common and simple in this kind of sentence
• 这个 = also possible, often a bit more specific

Because 这 is being used as a pronoun here, not as a determiner before a noun.

Compare:

1. 这是洗衣粉。
   = This is laundry detergent.
   Here 这 stands alone, so no measure word is needed.

2. 这袋是洗衣粉。
   = This bag is laundry detergent.

3. 这包洗衣粉。
   = This bag/package of laundry detergent.
   Here 这 is directly modifying a noun, so a measure word is usually needed.

So the short answer is: when 这 means this by itself, no measure word is required.

洗衣粉 is a compound word:

• 洗 = wash
• 衣 = clothes
• 粉 = powder

So literally it is something like clothes-washing powder.

That is why it means laundry detergent or more literally washing powder.

This is a very common feature of Chinese vocabulary: many words are built from smaller meaningful parts.

Strictly speaking, 洗衣粉 most literally means washing powder, so it usually refers to powder detergent.

If you want to talk about laundry detergent more generally, you may also see:

• 洗衣液 = liquid laundry detergent
• 洗衣剂 = laundry detergent/cleaning agent

But in everyday use, 洗衣粉 is very common and learners will often first meet it as laundry detergent.

The pinyin is xǐyīfěn.

Tone by tone:

• 洗 = xǐ → 3rd tone
• 衣 = yī → 1st tone
• 粉 = fěn → 3rd tone

A rough pronunciation guide:

• xǐ sounds somewhat like shee with the tongue positioned farther back than English sh
• yī sounds like ee
• fěn sounds roughly like fun, but not exactly

So: xǐ-yī-fěn

Yes, there is one very common tone change to notice.

这 is normally written with a 4th tone: zhè.
But when 一 and 不 are involved, people often ask about tone changes; here the important one is actually pronunciation flow, not a spelling change.

Also, when two 3rd tones come together, pronunciation can shift in connected speech. In 洗衣粉, the first and third syllables are 3rd tone, but they are not directly next to each other, so there is no special two-3rd-tone sandhi pattern there.

In careful beginner speech, just pronounce:

• zhè shì xǐ yī fěn

That is perfectly fine.

Because this sentence is a basic A 是 B identification sentence.

The pattern is:

A 是 B
= A is B

So:

• 这 = A
• 洗衣粉 = B

This makes the word order very straightforward for English speakers in this case.

However, not all Chinese sentences match English so closely. This one just happens to be a simple example.

No, that would sound wrong.

洗衣粉 is generally an uncountable substance noun here, like detergent or powder, so you do not normally say:

• 这是个洗衣粉

The measure word 个 is not appropriate in this sentence.

You would say:

• 这是洗衣粉。 = This is laundry detergent.
• 这是一袋洗衣粉。 = This is a bag of laundry detergent.
• 这是一盒洗衣粉。 = This is a box of laundry detergent.

So if you want to count the container, use a suitable measure word and noun such as 袋 or 盒.

Not in this sentence.

If you want to say This is laundry detergent, you need 是:

• 这是洗衣粉。

Without 是, 这洗衣粉 does not work as a normal complete sentence meaning This is laundry detergent.

Chinese sometimes omits elements that English requires, but in this basic noun-equals-noun sentence, 是 should be there.

Yes, it is natural if you are identifying something, for example:

• pointing to a product in a store
• explaining what a container holds
• correcting someone who thought it was something else

For example:

• A: 这是糖吗？
• B: 不是，这是洗衣粉。
  Is this sugar?
  No, this is laundry detergent.

So the sentence is especially natural when distinguishing one substance from another.

The only difference is distance from the speaker.

• 这 = this
• 那 = that

So:

• 这是洗衣粉。 = This is laundry detergent.
• 那是洗衣粉。 = That is laundry detergent.

Use 这 for something near you, and 那 for something farther away.

Chinese uses its own punctuation marks in standard writing.

The symbol 。 is the Chinese full stop, equivalent to the English period .

So:

• 这是洗衣粉。

is just the normal written way to end the sentence in Chinese.