هذا الحي هادئ في الصباح، لكنه ليس هادئا في المساء.

This neighborhood is quiet in the morning, but it is not quiet in the evening.

Breakdown of هذا الحي هادئ في الصباح، لكنه ليس هادئا في المساء.

• هذا: this
• في: in
• المساء: evening
• الصباح: morning

Questions & Answers about هذا الحي هادئ في الصباح، لكنه ليس هادئا في المساء.

Where is the word is in هذا الحي هادئ?

In Arabic, a present-tense sentence like this neighborhood is quiet usually has no separate word for is. So هذا الحي هادئ is literally this neighborhood quiet, but it means this neighborhood is quiet.

That is very normal in Arabic.
When Arabic wants to negate this kind of sentence, it often uses ليس, which is why the second clause says ليس هادئًا.

Why is it هذا الحي and not هذا حي?

Because هذا الحي means this neighborhood: the demonstrative هذا is directly modifying a definite noun.

In standard Arabic, when هذا / هذه means this before a specific noun, that noun is usually also definite with الـ:

• هذا الحي = this neighborhood
• هذا البيت = this house

Without الـ, the structure usually changes:

• هذا حيٌّ would normally be understood more like this is a neighborhood

So هذا الحي is the normal form here.

Why do we use هذا and not هذه?

Because الحيّ is a masculine singular noun.