kono tyoukoku ha ookii desu.

彫刻 is read ちょうこく.

In this sentence, it means sculpture. Depending on context, 彫刻 can also refer more broadly to carving or sculptural work, but here it is being used as a noun: a sculpture.

この means this when it comes directly before a noun.

• この 彫刻 = this sculpture

By contrast, これ means this one / this thing and stands by itself.

So:

• この 彫刻 は 大きいです。 = This sculpture is big.
• これ は 大きいです。 = This is big.

A common learner rule is:

• この / その / あの
  • noun
• これ / それ / あれ = stand alone

は marks the topic of the sentence.

So in:

• この 彫刻 は 大きいです。

the topic is この 彫刻 = this sculpture.

The rest of the sentence, 大きいです, says something about that topic: it is big.

A very natural way to think about it is:

• As for this sculpture, it is big.

This is why は is often translated as is in beginner materials, but it is not literally the same as the English verb to be. It is a topic marker.

When は is used as a particle, it is pronounced wa.

So:

• この 彫刻 は 大きいです。 is pronounced roughly:
• kono chōkoku wa ōkii desu

This is just a special pronunciation rule for the particle は. The character は is normally read ha in regular words, but as a topic particle it is read wa.

Yes, 大きい can already function as a predicate by itself.

So both of these are grammatical:

• この 彫刻 は 大きい。
• この 彫刻 は 大きいです。

The difference is mainly politeness:

• 大きい = plain style
• 大きいです = polite style

This is a very common pattern with い-adjectives in modern Japanese.

Yes, 大きいです is perfectly normal in modern Japanese.

It is true that い-adjectives do not need です to be grammatical. For example:

• 大きい。 = It is big.

But adding です makes it polite:

• 大きいです。 = It is big. polite

So です here is not turning the adjective into a noun or changing its basic meaning; it is mainly adding politeness.

Japanese does not normally use articles like a, an, and the.

So 彫刻 can mean:

• a sculpture
• the sculpture
• just sculpture

The exact meaning depends on context.

In this sentence, この already makes it specific:

• この 彫刻 = this sculpture

So no article is needed.

Japanese sentence structure works differently from English.

In English:

• This sculpture is big.

In Japanese:

• この 彫刻 は 大きいです。

The adjective 大きい already carries the descriptive meaning big and can serve as the main predicate. Then です adds politeness.

So Japanese does not need a separate word exactly like English is in this kind of sentence.

It could, but the nuance would change.

• この 彫刻 は 大きいです。
  = As for this sculpture, it is big.
  This is neutral and natural if you are talking about the sculpture as the topic.

• この 彫刻 が 大きいです。
  This sounds more like This sculpture is the big one or It is this sculpture that is big, depending on context.

So は is the more straightforward choice for a simple statement like This sculpture is big.

大きい is an い-adjective.

A quick sign of an い-adjective is that it ends in い in its dictionary form.

Examples:

• 大きい = big
• 小さい = small
• 新しい = new

This matters because い-adjectives change in their own way:

• 大きい = big
• 大きくない = not big
• 大きかった = was big
• 大きくなかった = was not big

Normally, Japanese is written without spaces:

この彫刻は大きいです。

The spaced version is often used in beginner materials to make the parts easier to see:

• この
• 彫刻
• は
• 大きい
• です

But in real Japanese writing, you would usually see:

この彫刻は大きいです。

Yes, it is natural and correct.

この彫刻は大きいです。 is a standard, polite sentence meaning This sculpture is big.

Depending on context, a native speaker might also say things like:

• この彫刻は大きい。 plain
• この彫刻、大きいですね。 conversational, with a softer tone
• この彫刻は大きいな。 casual, expressive

But the original sentence is absolutely fine.

You make 大きい negative by changing it to 大きくない.

So:

• この彫刻は大きくないです。 = This sculpture is not big.

You may also see:

• この彫刻は大きくありません。

Both are polite.
Very roughly:

• 大きくないです = common polite negative
• 大きくありません = more formal-sounding polite negative

A polite question version is:

この彫刻は大きいですか。
= Is this sculpture big?

You just add か at the end in formal or textbook-style Japanese.

In casual speech, people often use rising intonation instead:

• この彫刻は大きい？
• この彫刻は大きいですか？ is still perfectly normal and polite.