Nad psacím stolem je police.

In this sentence, police means shelf.

It is a very common false friend for English speakers:

• police = shelf
• policie = police, police force

So Nad psacím stolem je police. means there is a shelf above the desk, not anything to do with the police.

Nad means above or over.

In this sentence, it shows location:

• nad psacím stolem = above the desk

So the sentence describes where the shelf is.

Because nad here requires the instrumental case when it describes a stationary location.

The basic form is:

• stůl = desk, table

But after nad in this kind of sentence, it changes to instrumental:

• stolem = above the desk / over the desk

So:

• nad stolem = above the desk

Because adjectives in Czech must agree with the noun they describe in:

• gender
• number
• case

Here, psací describes stůl. Since stůl becomes stolem in the instrumental singular, the adjective must also change:

• psací stůl = writing desk
• psacím stolem = above the writing desk

So psacím is the instrumental singular form that matches stolem.

Literally, psací stůl means writing table.

In natural English, that is usually:

• desk
• writing desk

So in this sentence, psacím stolem refers to a desk, not just any table.

Both are grammatical, but the emphasis is different.

• Nad psacím stolem je police.
  This starts with the location and sounds like Above the desk, there is a shelf.
• Police je nad psacím stolem.
  This starts with the shelf and sounds more like The shelf is above the desk.

Czech word order is more flexible than English. The version in your sentence is a very natural way to introduce or describe what is in a place.

Czech does not have articles like English a/an and the.

So police can mean:

• a shelf
• the shelf

And psací stůl can mean:

• a desk
• the desk

The exact meaning depends on context. In many textbook translations, this sentence is rendered as There is a shelf above the desk or Above the desk is a shelf.

Yes. Je is the 3rd person singular present form of být, which means to be.

So:

• je = is

In this sentence:

• je police = is a shelf / there is a shelf

Unlike in some other Slavic languages, Czech normally keeps this verb in the present tense, so je is needed in a standard sentence like this.

Police is a feminine noun.

That matters for agreement in other sentences, for example:

• ta police = that shelf
• nová police = a new shelf

You do not see the gender clearly in je, because je is the same for all singular genders in the present tense.

It can take another case depending on meaning.

With location (no movement), nad takes the instrumental:

• nad stolem = above the desk

With movement toward a position above something, it can take the accusative:

• nad stůl = to above the desk

So in your sentence, nad psacím stolem uses the instrumental because the shelf is already there; nothing is moving.

No, it is pronounced very differently.

Approximate pronunciation:

• police ≈ PO-li-tse
• psacím ≈ PSA-tseem

A few useful points:

• Czech stress is usually on the first syllable.
• c in Czech is pronounced like ts.
• The final e in police is pronounced, not silent.
• í is a long vowel.

So police does not sound like English police.