Lögreglan talar við fangann.

Because Icelandic lögregla is a singular feminine noun meaning police or police force. So unlike English, where the police behaves like a plural expression, Icelandic treats it as a singular noun in sentences like this.

That is why the verb is singular too:

• Lögreglan talar = The police is/are speaking
• literally, the grammar is singular

So in Icelandic, lögreglan is grammatically more like the police force than English the police.

The ending -an is the definite article attached to the noun. Icelandic usually puts the on the end of the word instead of using a separate word.

So:

• lögregla = police
• lögreglan = the police

This is very common in Icelandic. Compare:

• maður = man
• maðurinn = the man

The exact form of the article changes depending on the noun’s gender, number, and case.

Because the subject is third person singular: lögreglan.

The verb að tala means to speak / to talk, and in the present tense it changes according to person and number:

• ég tala = I speak
• þú talar = you speak
• hann/hún/það talar = he/she/it speaks
• við tölum = we speak
• þið talið = you speak
• þeir/þær/þau tala = they speak

Since lögreglan is singular, Icelandic uses talar.

Here við means with or to, in the sense of speaking to someone.

So:

• tala við einhvern = talk to / speak with someone

This is just the normal Icelandic construction. English can say:

• talk to the prisoner
• talk with the prisoner

Icelandic uses við for that idea:

• Lögreglan talar við fangann.

You normally do not say Lögreglan talar fangann.

Yes. Fangann is the definite accusative singular form of fangi (prisoner).

The base noun is:

• fangi = prisoner

In this sentence, it comes after the preposition við, and við takes the accusative case. Also, the noun is definite (the prisoner), so both things affect the form.

So the chain is roughly:

• fangi = prisoner
• accusative singular: fanga
• definite accusative singular: fangann = the prisoner

This is a very common thing in Icelandic: the noun changes form because of case and definiteness.

It is in the accusative singular.

Why? Because the preposition við governs the accusative. In Icelandic, prepositions often require a specific case, and learners usually have to memorize that.

So in this sentence:

• við
  • accusative
• therefore fangi becomes fangann

A useful thing to remember is that Icelandic cases are often triggered by:

• prepositions
• verbs
• sentence role
• whether a noun is definite or indefinite

Because Icelandic usually expresses the as a suffix attached to the noun.

So instead of a separate word like English the prisoner, Icelandic often uses one word:

• fangann = the prisoner

This happens with both nouns in the sentence:

• lögreglan = the police
• fangann = the prisoner

So one important habit in Icelandic is to look at the endings of nouns, because they often contain information that English puts in separate words.

Yes, that is a very good idea.

It is helpful to learn many Icelandic verbs together with the preposition they commonly use. Here:

• tala við = talk to / speak with

If you learn just að tala, you know the basic meaning to speak, but you may still not know how to say speak to someone naturally. Learning the whole pattern is better:

• að tala við einhvern = to speak with someone

This is especially important in Icelandic because the preposition often determines the case too.

The sentence has the normal main-clause order:

• Lögreglan = subject
• talar = verb
• við fangann = prepositional phrase

So it is basically:

Subject + Verb + Prepositional phrase

That is the most neutral order here.

Icelandic word order can be more flexible than English because case endings help show what each word is doing, but this sentence is straightforward and neutral.

A rough English-friendly guide would be:

• lögreglan ≈ LUR-grekh-lan or LÖG-reg-lan
• fangann ≈ FAHN-gan

A few pronunciation notes:

• ö is not like normal English o. It is closer to the vowel in some pronunciations of bird or German ö, though not exactly the same.
• g in Icelandic can sound softer than English g, depending on its position.
• The stress is usually on the first syllable: LÖGreglan, FANgann.

If you are learning pronunciation seriously, it is best to listen to native audio, because Icelandic spelling and sound do not always match English expectations very closely.