دوست من امروز در مدرسه است.

My friend is at school today.

Breakdown of دوست من امروز در مدرسه است.

• دوست: friend
• من: my / I
• بودن: to be
• مدرسه: school
• امروز: today
• در: in

Questions & Answers about دوست من امروز در مدرسه است.

Why is it دوست من and not دوستِ من? Is something missing?

In writing, the ezâfe vowel (ـِ / -e) is usually not shown, but it’s still pronounced: doost-e man = my friend.
So دوست من is read as دوستِ من even though the vowel isn’t written.

How do you pronounce the whole sentence?

A common natural pronunciation is: doost-e man emruz dar madrese ast.

• دوستِ من = doost-e man
• امروز = emruz
• در = dar
• مدرسه = madrese
• است = ast (often reduced in speech)

What does در mean here, and why is it used for at/in?

در basically means in and is also used for at in many contexts. For locations like school, home, the office, Persian often uses در + place where English might say at:

• در مدرسه = at school / in school (context decides the best English choice)

Is است always necessary? Can you leave it out?

In formal written Persian, است is often included. In everyday speech, it’s very commonly dropped or reduced:

• Formal: دوست من امروز در مدرسه است.
• Casual: دوست من امروز در مدرسه‌ست. (joined form of است)
• Very casual: دوست من امروز در مدرسه. (copula omitted; context supplies is)

Why does the verb come at the end?

Persian is typically SOV (Subject–Object–Verb) or more generally verb-final. Even with “to be,” the copula often appears at the end:

• [دوست من] [امروز] [در مدرسه] است
  = My friend
  • today
    • at school
      • is

Can I move امروز to a different position?

Yes. Time words are flexible, especially in speech. These are all possible, with slightly different emphasis:

• دوست من امروز در مدرسه است. (neutral)
• امروز دوست من در مدرسه است. (emphasizes today)
• دوست من در مدرسه است امروز. (possible, but less common / more emphatic or conversational)

Does مدرسه mean a school or the school?

By itself, مدرسه can be interpreted as school in a general sense (like English at school) or as a specific school from context. Persian doesn’t require the/a the same way English does. If you want to make it clearly definite, you might add something like:

• اون مدرسه = that school
• مدرسهٔ ما = our school

Why isn’t there a word for a/the in the sentence?

Persian doesn’t use articles the way English does. Indefiniteness can be shown with یک (a/one) or -ی (-i) in many contexts, but it’s often left unmarked when the meaning is general or obvious:

• دوست من امروز در یک مدرسه است. = …in a school (more specific/odd unless context supports it)
• در مدرسه often naturally means at school (general activity/location)

Could I say دوستم instead of دوست من?

Yes. دوستم is the attached form meaning my friend:

• دوست من = doost-e man (a bit more explicit/formal)
• دوستم = doost-am (very common in speech)
  So you can say: دوستم امروز در مدرسه است.

Why isn’t را used anywhere?

را marks a definite direct object. This sentence has no direct object—در مدرسه is a location phrase, not an object—so را is not used.
You’d use را in something like: دوستم را دیدم = I saw my friend.

How would you make it negative: My friend is not at school today?

You typically negate the copula:

• دوست من امروز در مدرسه نیست. = My friend isn’t at school today.
  (نیست = is not)

Is this sentence formal, casual, or neutral?

It’s neutral-to-formal mainly because it uses است as a separate word. In casual speech you’d more often hear:

• دوست من امروز مدرسه‌ست. (often even dropping در)
  But your original sentence is perfectly correct and common in writing and careful speech.