این دوست من است.

• این = this (a demonstrative: “this”)
• دوست = friend
• من = me / my (here it means my because it follows a noun)
• است = is (3rd person singular of “to be” in formal/written Persian)

So the structure is literally: this + friend + of me + is → “This is my friend.”

Persian often expresses possession by placing a pronoun after the noun:

• دوستِ من = “my friend” (literally “friend of me”)

So من is still “me,” but the pattern noun + (ezāfe) + pronoun functions like “my/your/his…” in English.

That -e is the ezāfe (ـِ), a linking vowel that connects a noun to what follows it (like a possessor or an adjective).

• Written without vowel marks: دوست من
• Pronounced: دوستِ من (doost-e man)

In everyday Persian text, short vowels (including ezāfe) are usually not written, but they’re spoken.

• In formal/written Persian, است is common: این دوست من است.
• In colloquial speech, it’s often shortened or omitted:
  • این دوست منه. (very common)
  • این دوستمه. (even more compact: “This is my friend.”)
  • Sometimes just: این دوستِ منه. (with clear ezāfe in speech)

So the full است version is correct and slightly more formal.

Yes, but there’s a nuance:

• است is more formal/written.
• هست is more neutral/spoken and can sound a bit more “existence-like,” but it’s also used as “is” in speech.

Examples:

• Formal: این دوست من است.
• Spoken: این دوست منه / این دوست من هست.

The most common neutral order is exactly what you have:

• این دوست من است.

But Persian allows variations for emphasis:

• این، دوستِ من است. = “This is my friend.” (slight pause/emphasis on this)
• دوستِ من این است. = “My friend is this one.” (emphasis on identifying which one)

All are grammatical; they just shift focus.

You can make a yes/no question mainly with intonation:

• این دوستِ من است؟ = “Is this my friend?”

In speech you might hear:

• این دوستِ منه؟
• این دوستِ من هست؟

You can also add آیا (formal “whether/indeed”) in writing:

• آیا این دوستِ من است؟

Use نیست (“is not”):

• این دوستِ من نیست. = “This is not my friend.”

Colloquial:

• این دوستِ من نیست. (same in speech)
• این دوستِ من نیس. (informal pronunciation)

Common options:

• این‌ها دوستانِ من هستند. (formal/plural “are”)
• این‌ها دوست‌هایِ من هستند. (also possible; often used when emphasizing “my friends” as a set)

Spoken:

• این‌ها دوستایِ منن. (very common colloquial plural)

Note: دوستان is a common plural for دوست (“friends”).

A natural pronunciation (with the unwritten ezāfe) is roughly:

• in doost-e man ast

And in everyday speech, you’ll often hear:

• in doost-e mane → written as این دوست منه
• in doostame → written as این دوستمه (the -e man compresses into -am)