Policie našla jejich tašku.

Because Policie is grammatically singular feminine in Czech.

So the past tense verb has to agree with the subject:

• policie = feminine singular
• našla = feminine singular past form of najít (to find)

Even though English the police often feels plural, Czech policie is treated as a singular noun here.

Compare:

• Policie našla tašku. = The police found the bag.
• Policisté našli tašku. = The police officers found the bag.

In the second sentence, policisté is masculine plural, so the verb becomes našli.

Tašku is in the accusative singular because it is the direct object of the verb našla.

The dictionary form is:

• taška = bag

But after a transitive verb like najít (to find), the thing being found goes into the accusative:

• nominative: taška
• accusative: tašku

This is a very common pattern with feminine nouns ending in -a:

• kniha → knihu
• žena → ženu
• taška → tašku

Jejich means their.

It shows possession:

• jejich taška = their bag

A useful thing to know is that jejich refers to them (3rd person plural), and in standard Czech it does not change its form the way many other possessives do.

So you can see the same jejich in many contexts:

• jejich dům = their house
• jejich auto = their car
• jejich taška = their bag

The noun after it still changes case as needed, but jejich itself stays the same.

Czech does not use articles like English a and the.

So:

• Policie našla jejich tašku.

can naturally mean:

• The police found their bag.

English needs an article, but Czech does not. Definiteness is usually understood from context.

That is why Czech learners of English often forget articles, and English speakers learning Czech often look for them when they are not there.

In this sentence, policie is grammatically singular.

That can feel strange to English speakers, because English police often behaves like a plural idea:

• The police are here.

But in Czech:

• policie je tady = the police is/are here in meaning, but grammatically singular
• policie našla... = singular verb form

If you want an explicitly plural subject in Czech, you would use something like:

• policisté = police officers
• policajti = cops (informal)

Then the verb would be plural.

The infinitive is najít, which means to find.

So:

• najít = to find
• našla = found (feminine singular past)

This verb can look a little irregular to learners because the forms are not all built from exactly the same visible stem:

• infinitive: najít
• masculine past: našel
• feminine past: našla
• imperative: najdi

So yes, it is normal if našla does not immediately look like najít to you.

In Czech, the past tense is built differently from English.

In the 3rd person, Czech usually just uses the past participle form by itself:

• našel = he found
• našla = she/it found
• našli = they found

So in this sentence:

• Policie našla jejich tašku.

there is no separate word meaning did or has.

In other persons, Czech does use auxiliary forms:

• našel jsem = I found
• našla jsi = you found

But in the 3rd person, that auxiliary is not expressed.

Czech word order is much more flexible than English word order because the endings already show the grammar.

So this sentence can be rearranged:

• Policie našla jejich tašku.
• Jejich tašku našla policie.
• Našla jejich tašku policie.

These all keep roughly the same basic meaning, but the focus or emphasis changes.

The original order:

• Policie našla jejich tašku.

is a very neutral, straightforward way to say it.

Because English relies more on word order, these changes can be harder for English speakers at first.

No. Tašku is singular accusative, so it means bag in the singular.

So:

• jejich tašku = their bag

If it were plural, the noun would look different, for example:

• jejich tašky can mean their bags in some contexts, depending on case
• in accusative plural for inanimate feminine nouns, the form is also tašky

So in this sentence, the form clearly points to one bag.

Not necessarily. It is capitalized here because it is the first word of the sentence.

Normally, policie is a common noun and is written with a lowercase p:

• policie přijela = the police arrived

It would only be capitalized in the middle of a sentence if it were part of an official name, such as the name of an institution.

So in this sentence, the capital P does not by itself tell you that it is a proper noun.