رستورانی که در این خیابان است تمیز است.

The -ی here is the indefinite marker. So رستوران means restaurant, and رستورانی means a restaurant or sometimes a certain restaurant.

In sentences with a relative clause, Persian often uses this form even when English would naturally say the restaurant that.... So رستورانی که در این خیابان است can be understood as the restaurant that is on this street or a restaurant that is on this street, depending on context.

So the -ی does not always translate neatly as English a/an.

که is the relative word that / which / who.

In this sentence, it connects رستورانی to the description that follows:

• رستورانی = a/the restaurant
• که در این خیابان است = that is on this street

So:

• رستورانی که در این خیابان است = the restaurant that is on this street

A useful thing to remember is that Persian uses که for people and things alike. Unlike English, it does not change to who, which, or that.

Persian often puts extra descriptive information before the main statement is completed.

Literal structure:

• رستورانی = a/the restaurant
• که در این خیابان است = that is on this street
• تمیز است = is clean

So the whole sentence is literally:

• A/The restaurant that is on this street clean is

Natural English rearranges it as:

• The restaurant that is on this street is clean

This is normal Persian sentence structure. The relative clause comes right after the noun it describes.

Because there are really two clauses in the sentence:

1. که در این خیابان است = that is on this street
2. تمیز است = is clean

The first است belongs to the relative clause and tells you where the restaurant is.
The second است is the main verb of the whole sentence and tells you that it is clean.

So each است has its own job.

Persian does not have a direct equivalent of the English definite article the.

Whether a noun is understood as a restaurant or the restaurant usually depends on:

• context
• word order
• modifiers like relative clauses
• whether the speaker assumes the listener can identify it

So Persian often leaves definiteness unmarked, and English has to choose a or the when translating.

That is why رستورانی که در این خیابان است can sound like the restaurant that is on this street in context, even though there is no separate word for the.

در means in or at.

• این خیابان = this street
• در این خیابان = in/on this street

English usually says on this street, but Persian commonly uses در in this kind of location expression.

So even though the literal meaning is closer to in this street, the natural English translation is often on this street.

Because که introduces a relative clause, and relative clauses do not take ezafe in front of که.

Compare:

• رستورانِ تمیز = the clean restaurant
  Here تمیز is just an adjective, so ezafe is used.

But:

• رستورانی که در این خیابان است = the restaurant that is on this street
  Here که در این خیابان است is a whole clause, not just a single adjective, so there is no ezafe before که.

That difference is very important.

Yes, رستورانی که در این خیابان است تمیز است sounds fairly written or formal.

In everyday spoken Persian, you are more likely to hear something like:

• رستورانی که توی این خیابون هست تمیزه

Common spoken changes:

• در → توی
• خیابان → خیابون
• است → هست or ـه
• تمیز است → تمیزه

So the written sentence is correct, but the spoken version is more natural in conversation.

A careful written-style pronunciation is approximately:

resturâni ke dar in xiyâbân ast tamiz ast

A more everyday spoken pronunciation might sound closer to:

resturâni ke tuye in xiyâbun haste tamize

A few notes for English speakers:

• خ is like a throaty kh
• ی in این sounds like ee in many pronunciations, though the whole word is just in
• final است is often reduced in speech

It can function either way depending on context, but in a sentence like this, English often prefers the restaurant that....

Why? Because the relative clause که در این خیابان است identifies which restaurant is being talked about. Once you specify it that way, English tends to make it definite:

• the restaurant that is on this street

But Persian does not always mark that distinction as sharply as English does. So the Persian form with -ی can still be used.

A good learner takeaway is:

• do not force Persian -ی to equal English a/an every time

It is possible in some contexts, but رستورانی که... is more natural here.

Using رستورانی makes the noun sound smoother and more typical in this kind of relative-clause structure. It often introduces an item being identified by the clause that follows.

So for a learner, رستورانی که در این خیابان است تمیز است is the safer pattern to remember.

In speech, there is often a slight pause after the relative clause:

• رستورانی که در این خیابان است، تمیز است.

In writing, the comma is optional. Persian punctuation is often less rigid than English in such sentences.

The important thing is to understand the structure:

• [رستورانی که در این خیابان است] = noun + relative clause
• [تمیز است] = main statement

So whether or not a comma is written, the meaning stays the same.