zhèjiàn yīfu búyòng shǒuxǐ.

件 is a measure word (also called a classifier) for items of clothing and some other objects.

In Mandarin, when you say this / that / one / two plus a noun, you usually need a measure word between them:

• 这件衣服 = this item of clothing
• 一件衣服 = one piece of clothing
• 那件外套 = that coat

So the pattern is:

这 + measure word + noun

Here, 件 is the natural measure word for 衣服.

Mandarin normally requires a measure word after demonstratives like 这 (this) and 那 (that) when they directly modify a noun.

So:

• 这件衣服 = correct
• 这衣服 = usually not standard in normal Mandarin

The basic structure is:

这 / 那 + measure word + noun

English does not need this extra word, but Mandarin usually does.

Because 这件 is directly modifying 衣服, and with demonstratives plus measure words, 的 is normally not used.

So you say:

• 这件衣服
• 那本书
• 这双鞋

not:

• 这件的衣服 ❌

A simple way to remember it:
when you have this/that + measure word + noun, you usually do not add 的.

This is a very common pronunciation rule in Mandarin.

Normally, 不 is fourth tone: bù.
But when it comes before another fourth-tone syllable, it changes to second tone: bú.

Here:

• 用 is fourth tone: yòng
• so 不 + 用 becomes búyòng

More examples:

• 不是 → bú shì
• 不要 → bú yào
• 不对 → bú duì

This is a tone sandhi rule, used for smoother pronunciation.

In modern Mandarin, the second syllable of 衣服 is usually pronounced with a neutral tone:

• 衣服 = yīfu

This is very common in everyday words of two syllables, where the second syllable becomes lighter and shorter.

So even though 服 by itself has a full tone in other contexts, in 衣服 it is usually neutral.

Here, 不用 means there is no need to or doesn't need to.

So in this sentence, it means the clothing does not need hand washing.

That is a little different from a strong prohibition like must not.

Compare:

• 不用手洗 = no need to wash by hand
• 不能手洗 = cannot be washed by hand
• 别手洗 = don't wash it by hand

So 不用 focuses on lack of necessity, not necessarily impossibility.

手洗 literally means hand-wash:

• 手 = hand
• 洗 = wash

Together, they form a verb meaning to wash by hand.

In Chinese, it is common to combine a noun and a verb like this to make a more specific action:

• 手洗 = wash by hand
• 机洗 = machine wash
• 水洗 = wash with water

So 不用手洗 means doesn't need to be hand-washed.

Because 手洗 and 洗手 mean different things.

• 手洗 = to wash something by hand
• 洗手 = to wash your hands

This difference comes from word order and function:

• in 手洗, 手 describes the method: hand-wash
• in 洗手, 手 is the object: wash hands

So in this sentence, 手洗 is correct because it describes how the clothing is washed.

Yes. Mandarin nouns usually do not change form for singular and plural the way English nouns do.

So 衣服 can mean:

• clothing in general
• clothes
• a garment / an item of clothing

In this sentence, the measure word 件 tells you we are talking about one item:

• 这件衣服 = this piece of clothing / this garment

So even though 衣服 can be broad in meaning, 件 makes it specific.

Yes, you can think of the sentence as having an understood subject depending on context.

这件衣服不用手洗。 literally is something like:

This clothing item doesn't need hand-washing.

In natural English, we might say:

• This shirt doesn't need to be hand-washed.
• You don't need to hand-wash this item.

Mandarin often allows this kind of flexible interpretation without adding extra words like it or you, as long as the meaning is clear from context.

Yes. Those are both possible, but the nuance is slightly different.

• 不用手洗 = very common, natural, conversational
• 不需要手洗 = a bit more explicit: does not require hand washing
• 不必手洗 = more formal or written: it is unnecessary to hand-wash

All three are understandable, but 不用 is probably the most everyday phrasing here.

Not automatically. It only clearly says that hand washing is not necessary.

Depending on context, it might imply:

• machine washing is okay
• some other cleaning method is okay
• special care is not needed

But strictly speaking, 不用手洗 only tells you one thing: hand washing is not required. It does not by itself guarantee exactly what method should be used instead.