Poliția arestează criminalul.

Because Romanian usually puts the definite article at the end of the noun instead of using a separate word before it.

In this sentence:

• poliție = police
• poliția = the police
• criminal = criminal
• criminalul = the criminal

So Romanian often says the equivalent of police-the and criminal-the.

The ending changes depending on the noun’s gender and number.

In Romanian, poliția is a singular noun referring to the institution or police force. So the verb is also singular:

• Poliția arestează... = The police arrests / is arresting... in Romanian grammar

In natural English, we usually say the police are, but Romanian treats poliția as one entity.

If you want to talk about the individual police officers, you would use a different word:

• polițiștii = the police officers

Arestează is the 3rd person singular present tense of the verb a aresta = to arrest.

So:

• a aresta = to arrest
• arestează = he/she/it arrests, or is arresting

It agrees with poliția, which is grammatically singular.

It can mean either one, depending on context.

Romanian present tense often covers both:

• The police arrests the criminal
• The police is arresting the criminal

English makes a stronger distinction between simple present and present continuous than Romanian does. Without more context, arestează can work for both.

The most basic reason is word order: Romanian commonly uses subject–verb–object, just like English in neutral sentences.

So:

• Poliția = subject
• arestează = verb
• criminalul = direct object

That gives: The police arrest(s) the criminal.

Context and real-world meaning also help. It is much more natural that the police arrests the criminal than the other way around.

Very often, yes.

With a specific human direct object, Romanian frequently uses pe, and many speakers also add an object pronoun. A very natural version would be:

• Poliția îl arestează pe criminal.

Here:

• pe criminal marks the criminal as the direct object
• îl means him and often appears together with pe in natural Romanian

So the sentence you were given is understandable and useful as a simple learner example, but in everyday Romanian many speakers would prefer the version with pe (and often îl too).

Yes, Romanian word order is more flexible than English, especially when context makes the meaning clear.

But the sentence you have:

• Poliția arestează criminalul.

is the neutral, straightforward order.

As a beginner, this is the safest pattern to use:

• subject + verb + object

Romanian can move words for emphasis or style, but that is something to learn gradually.

Romanian often drops subject pronouns when they are not needed.

The verb form arestează already tells you that the subject is 3rd person singular, and the noun poliția is already present, so there is no need to add a separate pronoun.

This is very normal in Romanian.

A rough English-friendly pronunciation is:

po-lee-TSEE-a a-res-TEA-zuh kree-mee-NA-lul

A few important sounds:

• ț = ts as in cats
• ă = a short relaxed uh sound, somewhat like the last vowel in sofa
• ci in poliția is not like English sh; it is pronounced with ts because of ț

So:

• Poliția ≈ po-lee-TSEE-a
• arestează ≈ a-res-TEA-zuh
• criminalul ≈ kree-mee-NA-lul

The dictionary forms are:

• poliție = police
• a aresta = to arrest
• criminal = criminal

The sentence uses inflected forms:

• poliția = the police
• arestează = arrests / is arresting
• criminalul = the criminal

This is very common in Romanian: what you see in a sentence is often not the bare dictionary form.

Yes, they do.

The standard spelling is:

• Poliția arestează criminalul.

The marks in ț and ă are part of normal Romanian writing. If you leave them out:

• Politia aresteaza criminalul

people will still usually understand you, especially online, but it is not the proper standard spelling.

So it is best to learn and use the diacritics from the beginning.