הבית גדול, אבל החדר קטן.

Because the prefix ה־ is the Hebrew definite article, equivalent to English the.

• בית = house
• הבית = the house
• חדר = room
• החדר = the room

So in this sentence, both nouns are definite: the house and the room.

In Hebrew, adjectives usually come after the noun they describe.

So:

• הבית גדול = the house [is] big
• החדר קטן = the room [is] small

This is different from English, where adjectives usually come before the noun: the big house, the small room.

In this sentence, the structure is not big house but rather the house is big.

In present-tense Hebrew, there is usually no separate word for is / am / are in simple sentences like this.

So:

• הבית גדול literally looks like the house big
• but it means the house is big

And:

• החדר קטן literally looks like the room small
• but it means the room is small

This is completely normal in Hebrew.
If the sentence were in the past or future, Hebrew would use a form of to be.

Yes. Hebrew adjectives change to match the noun in gender and number.

Here:

• בית is a masculine singular noun
• חדר is also a masculine singular noun

So the adjectives also appear in the masculine singular form:

• גדול = big
• קטן = small

If the noun were feminine singular, the adjectives would usually end in ־ה:

• גדולה = big (feminine)
• קטנה = small (feminine)

For example:

• הדירה גדולה = the apartment is big

Great question. Hebrew handles adjectives differently depending on the sentence structure.

In your sentence:

• הבית גדול = the house is big

Here, גדול is part of the predicate, so it does not take ה־.

But if you want to say:

• the big house

then both the noun and adjective are definite:

• הבית הגדול

So compare:

• הבית גדול = the house is big
• הבית הגדול = the big house

That is a very important Hebrew distinction.

אבל means but.

It connects two contrasting ideas:

• הבית גדול = the house is big
• אבל = but
• החדר קטן = the room is small

So the whole sentence contrasts the size of the house with the size of the room.

A common pronunciation is:

ha-BA-yit ga-DOL, a-VAL ha-CHE-der ka-TAN

Word by word:

• הבית = ha-bayit
• גדול = gadol
• אבל = aval
• החדר = hacheder
• קטן = katan

A few helpful notes:

• The ח in החדר is a throaty sound, like the ch in German Bach or Scottish loch
• Stress is usually near the end:
  • baYIT
  • gaDOL
  • aVAL
  • cheDER
  • kaTAN

The prefix ה־ is usually pronounced ha-, but the exact sound can blend a little with the following consonant in normal speech.

In this sentence:

• הבית → ha-bayit
• החדר → usually ha-cheder or hacheder

Learners often notice that Hebrew spelling stays the same, while actual pronunciation can feel more connected and fluid in speech.

The main point is: ה־ marks definiteness, even if the spoken rhythm varies a bit.

Yes, but the version you have is the most neutral and straightforward.

Standard order here is:

• noun + adjective
• הבית גדול, אבל החדר קטן.

Hebrew can sometimes change word order for emphasis, but beginners should treat this version as the normal one.

So this sentence is a very good model for simple descriptive Hebrew.

Yes: the comma before אבל works very much like the comma before but in English.

So:

• הבית גדול, אבל החדר קטן.

This helps show the sentence has two linked parts:

1. הבית גדול
2. החדר קטן

joined by אבל = but.

Yes. This sentence is a classic example of describing something.

• הבית גדול describes the house
• החדר קטן describes the room

You are not saying what the house is; you are saying what it is like.

That is why adjectives are used:

• גדול = big
• קטן = small

This is one of the most basic and useful Hebrew sentence patterns: definite noun + adjective = the noun is adjective.