hakusyu ga ookii.

It is read はくしゅ が おおきい.

• 拍手（はくしゅ） = applause, clapping
• が = subject marker
• 大きい（おおきい） = big, large, loud

In normal Japanese writing, it would usually appear without spaces: 拍手が大きい。

Japanese is normally written without spaces, so the usual form is:

拍手が大きい。

Spaces are often added in textbooks or beginner materials to make the parts easier to see:

• 拍手
• が
• 大きい

They are just a learning aid.

拍手 is a noun. It means applause or clapping.

It usually refers to the act or sound of people clapping, not just one single clap. So in English, applause is often the best match.

が marks 拍手 as the thing being described.

The pattern is:

noun + が + adjective

So here, the sentence is saying that the applause has the quality 大きい.

This is a very common structure in Japanese:

• 音が大きい = The sound is loud.
• 声が大きい = The voice is loud.
• 拍手が大きい = The applause is loud.

That is a very common learner question. 大きい does literally mean big/large, but Japanese also uses it for volume.

So with sounds, 大きい often means loud:

• 音が大きい = The sound is loud.
• 声が大きい = The voice is loud.
• 音楽が大きい = The music is loud.

So 拍手が大きい means the applause is loud, strong, or big in volume/intensity.

In a sense, yes.

A learner might expect:

• 拍手の音が大きい = The sound of the applause is loud.

That is understandable, but Japanese often leaves out words that are obvious from context. So 拍手が大きい is a natural, shorter way to express the same basic idea.

You can think of it as:

• literally: the applause is big
• naturally: the applause is loud

Because 大きい is an い-adjective, and in Japanese, an い-adjective can be the predicate of a sentence all by itself.

So:

• 拍手が大きい。 = The applause is loud.

There is no separate word that must appear for is in this kind of sentence.

This is normal Japanese grammar:

• 部屋が広い。 = The room is spacious.
• 空が青い。 = The sky is blue.
• 拍手が大きい。 = The applause is loud.

Yes, 拍手は大きい is possible, but the nuance is different.

• 拍手が大きい: focuses on the applause as the subject of the description; a straightforward observation
• 拍手は大きい: makes 拍手 the topic and can sound contrastive, like As for the applause, it is loud

So if you are just describing what you notice, が is very natural.

Because 大きな拍手 and 拍手が大きい are doing different jobs.

• 大きな拍手 = a noun phrase, meaning big applause or a big round of applause
• 拍手が大きい = a full sentence, meaning the applause is loud

So:

• 大きな拍手をありがとう。 = Thank you for the big applause.
• 拍手が大きい。 = The applause is loud.

Yes, 拍手が大きい。 is plain style.

The polite version is:

拍手が大きいです。

Same meaning, different level of politeness.

You could, but the nuance changes.

• 大きい = loud in volume
• うるさい = noisy, too loud, annoyingly loud

So:

• 拍手が大きい = The applause is loud / strong.
• 拍手がうるさい = The applause is noisy / irritatingly loud.

If you only want to describe volume, 大きい is the better choice.

大きい is the non-past plain form.

In this sentence, it most naturally describes a present situation:

• The applause is loud.

If you want past tense, use:

• 拍手が大きかった。 = The applause was loud.

If you want polite past:

• 拍手が大きかったです。 = The applause was loud.