zhè shì yèpiàn.

In normal Chinese writing, there are no spaces between words. This sentence is normally written as:

这是叶片。

The spaces in your example are just a learning aid, to show the word breaks and match the pinyin.

这 means this.

In this sentence, it works like a pronoun: this is ...

So the structure is:

这 + 是 + 叶片
this + is + leaf blade / leaf

As a standalone word, 这 is very common when pointing something out.

Yes. The standard dictionary reading is zhè.

In everyday speech, especially before a classifier, many speakers say zhèi, for example:

这本书 → often pronounced zhèi běn shū

But here 这 stands alone, so zhè is the expected pronunciation.

是 is the verb used to link one noun phrase to another, like to be in sentences such as A is B.

So here it means:

这 = this
是 = is
叶片 = leaf blade / leaf

So the pattern is:

subject + 是 + noun

A very important point: 是 is mainly used when identifying or classifying something. It is not used the same way as English is in every sentence.

For example:

• 这是叶片。 = This is a leaf blade.
• 它很大。 = It is big.

Not 它是很大 in standard Mandarin.

Usually, no, not in a normal full sentence.

这是叶片。 is the standard sentence.

If you are just labeling a picture or diagram, you might see only:

叶片

That works as a label, but not as a full spoken sentence meaning This is a leaf blade.

That is a very good question.

For a single physical leaf, everyday Chinese often does use a measure word:

这是一片叶子。
这是一片叶片。

Here, 片 is the measure word.

So why does your sentence not have it? Because 这是叶片 sounds more like identifying a category or label, especially in a classroom, textbook, diagram, or science context.

So:

• 这是叶片。 = This is the leaf blade / This is a leaf blade.
  More like naming or identifying.
• 这是一片叶子。 = This is a leaf.
  More natural in everyday speech when talking about one actual leaf.

Both can relate to leaf, but they are not exactly the same in tone or usage.

• 叶子 is the everyday word for leaf
• 叶片 is more formal, scientific, or technical

叶片 can mean the leaf blade specifically, or a flat leaf-like piece in technical contexts.

So if you are just talking casually, 叶子 is often the more natural choice. If you are studying plant parts, 叶片 is very appropriate.

It is pronounced yèpiàn.

• 叶 = yè
• 片 = piàn

Both are 4th tone.

So the whole sentence is:

zhè shì yèpiàn

All four syllables are 4th tone. In careful pronunciation, that can sound very sharp and falling. In natural speech, native speakers usually smooth it out a bit, so not every syllable is equally strong, even though the tones are still correct.

Chinese does not have articles like English a, an, and the.

So 这是叶片 can mean:

• This is a leaf blade
• This is the leaf blade

The exact meaning depends on context.

Chinese usually leaves that information to the situation rather than marking it with a special word.

Two very common ways are:

这是叶片吗？
= Is this a leaf blade?

and

这是什么？
= What is this?

The first is a yes/no question using 吗.
The second asks for the identity of the object.

You would change 这 to 那:

那是叶片。

• 这 = this
• 那 = that

Everything else stays the same.