Hội này khá lớn.

Hội can have several meanings depending on context, such as:

• an association or organization
• a festival or fair
• a gathering or event

So the grammar of the sentence is straightforward, but the exact meaning of hội depends on what is being talked about.

In Vietnamese, words meaning this and that usually come after the noun, not before it.

So:

• hội này = this association / this festival
• nhà này = this house
• người này = this person

That word order is normal in Vietnamese.

Vietnamese often does not use a separate verb like English is before adjectives.

An adjective can act as the main predicate by itself:

• Nhà này đẹp. = This house is beautiful.
• Cô ấy cao. = She is tall.
• Hội này khá lớn. = This ... is quite large.

So the sentence is complete even without a separate word for is.

Khá means something like quite, rather, or fairly.

It shows a moderate degree:

• khá lớn = fairly large / quite big
• rất lớn = very large

So khá is usually less strong than rất.

Because degree words in Vietnamese normally come before the adjective they modify.

For example:

• khá lớn = quite big
• rất lớn = very big
• hơi lớn = a bit big

So Hội này khá lớn is correct.
Hội này lớn khá is not natural Vietnamese.

No. Lớn can describe more than literal physical size.

Depending on context, it can mean:

• big or large
• important or major
• grown-up or older in other situations

With hội, it usually refers to the scale or size of the group, event, or organization.

Usually yes.

Both lớn and to can mean big, but lớn is often more natural for things like:

• organizations
• events
• gatherings
• abstract scale or importance

To is more often used for physical size. So with hội, lớn is the more natural choice.

No, not here.

You can simply say:

• hội này

That is already natural and complete.

If you add cái and say cái hội này, it can sound more colloquial, emotional, or slightly dismissive, depending on tone and context. The neutral form is just hội này.

The pattern is:

noun + demonstrative + degree word + adjective

So here:

• hội = noun
• này = this
• khá = quite/fairly
• lớn = large

This is a very common Vietnamese structure.

Này usually modifies a noun and comes after it:

• hội này = this association / this festival

Đây usually stands alone and often means here or this is / this one:

• Đây là hội lớn. = This is a large association / festival.
• ở đây = here

So in this sentence, này is the right choice because it directly modifies hội.

You can replace khá with other degree words.

Stronger:

• Hội này rất lớn. = This ... is very large.
• Hội này cực kỳ lớn. = This ... is extremely large.

Weaker:

• Hội này hơi lớn. = This ... is a bit large.
• Hội này không lớn lắm. = This ... is not very large.

So khá gives a middle-strength description.

A rough guide is:

• Hội ≈ hoy with a heavy tone
• này ≈ nai / nye with a falling tone
• khá ≈ kha with a rising tone
• lớn ≈ lurn / luhn with a short ơ-type vowel

A good learner goal is not perfect imitation of English-like sounds, but remembering that each syllable has its own tone. In Vietnamese, the tones are an essential part of the word.