الإدارة في المبنى.

In Modern Standard Arabic, the present-tense verb to be is usually not written or spoken in simple sentences like this.

So الإدارة في المبنى literally looks like the administration in the building, but it naturally means The administration is in the building.

This is a very common Arabic pattern called a nominal sentence.

• الإدارةُ = the subject/topic of the sentence
• في المبنى = the predicate/comment telling where it is

In traditional Arabic grammar:

• الإدارةُ is the mubtadaʾ
• في المبنى is the khabar

Because the predicate is a prepositional phrase, the sentence expresses location.

الـ is the Arabic definite article, equivalent to the.

So:

• إدارة = an administration / administration
• الإدارة = the administration

In this sentence, the noun is definite, so it refers to a specific administration, office, or management department already known from context.

Because المبنى means the building, not just a building.

So:

• في مبنًى = in a building
• في المبنى = in the building

The sentence is talking about a specific building, not just any building.

A simple pronunciation guide is:

• الإدارة = al-idārah
• في = fī
• المبنى = al-mabnā

Together: al-idārah fī l-mabnā

A useful detail: in المبنى, the ل of الـ is pronounced clearly because م is a moon letter, not a sun letter.

The final ى is called alif maqṣūrah. At the end of a word, it usually represents a long ā sound.

So المبنى is pronounced al-mabnā, not al-mabnī.

This is an important spelling point for learners, because ى and ي look similar but do not sound the same here.

It would be:

الإدارةُ في المبنى

• الإدارةُ is nominative because it is the mubtadaʾ
• المبنى is genitive because it comes after the preposition في

One subtle point: المبنى is a noun ending in ى, so its case ending is not visibly shown at the end in normal spelling. Grammatically it is genitive, even though you do not see a final kasrah written there.

Yes. Arabic can move the prepositional phrase to the front for emphasis:

في المبنى الإدارةُ

This can mean something like The administration is in the building with extra focus on in the building.

However, الإدارة في المبنى is the more neutral and straightforward order for a learner to use first.