دوستی که دیروز در بازار دیدم، امروز در مدرسه است.

It breaks down like this:

• دوستی = a friend / a certain friend
• که دیروز در بازار دیدم = that/who I saw yesterday in the market
• امروز در مدرسه است = is at school today

So the whole structure is:

[noun] + [relative clause] + [main clause]

That is very common in Persian:

• دوستی = the noun being described
• که...دیدم = the description of that noun
• امروز در مدرسه است = what is being said about that noun

Yes, دوستی can also mean friendship in other contexts. But here it means a friend.

Why?

Because دوست means friend, and the ending -ی can mark indefiniteness, roughly like a or some in English.

So here:

• دوست = friend
• دوستی = a friend / some friend

Context tells you which meaning is intended. Since the rest of the sentence says who I saw yesterday... is at school today, it clearly refers to a person, not the abstract idea friendship.

که introduces a relative clause. Here it works like English who, that, or whom.

So:

• دوستی که... = a friend who/that...

Unlike English, Persian uses the same word که for people and things. It does not change the way English does:

• who
• whom
• that
• which

Persian just uses که and lets the rest of the sentence show the relationship.

Because Persian does not usually use a special relative pronoun like English whom.

In this sentence, که simply introduces the clause, and the role of دوستی is understood from the verb دیدم = I saw.

So literally, the structure is closer to:

• a friend that yesterday in the market saw-I

The listener understands that the friend is the person seen.

Persian often leaves that relationship to context and verb meaning instead of using a special form like whom.

Because the verb already includes the subject.

دیدم means I saw.

The ending -م tells you the subject is I.

So:

• دیدم = I saw
• دیدی = you saw
• دید = he/she saw
• دیدیم = we saw

Persian often drops subject pronouns when the verb ending already makes the subject clear.

So من is not necessary here.

Because Persian is generally a subject-object-verb language, and verbs usually come at the end of the clause.

In English you say:

• that I saw yesterday in the market

In Persian the verb comes later:

• که دیروز در بازار دیدم

This is normal Persian word order.

A rough word-for-word order would be:

• that yesterday in the market saw-I

That sounds strange in English, but it is natural in Persian.

Good question. A learner may expect something like:

• دوستی را که دیروز در بازار دیدم...

That version is also possible.

Here is the basic idea:

• را often marks a specific direct object.
• Without را, the noun can feel less specifically marked, or more like a certain friend rather than an explicitly definite object.

So:

• دوستی که... = a friend who... / a certain friend who...
• دوستی را که... = often more clearly the friend whom... or that friend who...

In real Persian, both patterns exist. The version without را is perfectly possible, especially in written Persian.

No. You do not use ezafe before که in this kind of relative clause.

So it is:

• دوستی که...

not:

• دوستیِ که...

Ezafe is used to connect nouns to adjectives, possessors, and some other modifiers, but relative clauses introduced by که attach directly without ezafe.

Compare:

• دوستِ خوب = a good friend
• دوستِ من = my friend
• دوستی که دیدم = a friend that I saw

So که does not need ezafe before it.

Because Persian usually puts the verb at the end of the clause, and است is the verb is.

So:

• امروز در مدرسه است = is at school today

A literal order would be:

• today at school is

That is normal in Persian.

This sentence is quite formal or neutral in style. In speech, است is often reduced or replaced, for example:

• امروز در مدرسه‌ست
• or in more conversational wording, something similar to امروز تو مدرسه‌ست

Sometimes, yes, but not always with exactly the same feel.

In many simple copular sentences, written Persian often uses است:

• در مدرسه است

هست can also mean is, but it often sounds a bit more emphatic or existential, depending on context.

In many everyday spoken situations, people often use:

• -ه / -ست instead of full است

So in speech, a learner is more likely to hear:

• مدرسه‌ست

For this written sentence, است is perfectly normal.

Persian does not have a definite article like English the.

So nouns often appear without any word corresponding to the, and context decides whether the meaning is definite or indefinite.

In this sentence:

• دوستی has -ی, which can give an indefinite sense: a friend / some friend
• بازار could mean the market or a market, depending on context
• مدرسه could mean the school, a school, or simply school, depending on context

So Persian relies much more on context than English does for article meaning.

در means in or at.

So:

• در بازار = in the market
• در مدرسه = at school / in school

In formal or written Persian, در is very normal.

In everyday speech, especially with common places, Persian often uses other prepositions or drops them in some expressions. For example, colloquial speech might prefer:

• تو بازار
• تو مدرسه

So the sentence as given is more formal/written in style.

A helpful pronunciation is:

doosti ke diruz dar bazaar didam, emruz dar madrese ast

A slightly more careful transliteration:

• doosti = دوستی
• ke = که
• diruz = دیروز
• dar bazaar = در بازار
• didam = دیدم
• emruz = امروز
• dar madrese ast = در مدرسه است

A few pronunciation notes:

• oo in doosti sounds like the vowel in food
• aa in bazaar is a long a
• didam is pronounced roughly dee-dam
• madrese is roughly ma-dre-se
• in connected speech, مدرسه است is often pronounced more like madrese-st

The comma is helpful, but it is not the most important part of the grammar.

It separates:

• the noun plus its relative clause: دوستی که دیروز در بازار دیدم
• from the main statement: امروز در مدرسه است

So it makes the sentence easier to read.

In Persian writing, punctuation is used, but people are not always as rigid about commas as English grammar textbooks may be. The sentence is still understandable without the comma, though the comma is a good choice here.