Ég tek lyklana úr vasanum og opna hurðina.

Tek is the 1st person singular present tense form of the verb taka (to take).

So:

• að taka = to take
• ég tek = I take / I am taking

Icelandic verbs change form depending on the subject and tense, so you normally cannot use the infinitive taka where English would use take.

In Icelandic, the definite article (the) is usually attached to the end of the noun instead of being a separate word.

So here:

• lyklar = keys

• lyklana = the keys

• vasi = pocket

• vasanum = the pocket

• hurð = door
• hurðina = the door

This is very normal in Icelandic. English uses a separate word (the), but Icelandic often uses an ending.

Because the sentence refers to the keys, not just keys in general.

Also, lyklana is in the accusative plural, because it is the direct object of tek (I take).

A rough breakdown:

• lyklar = keys (nominative plural)
• lyklana = the keys (accusative plural)

After many verbs, including taka, the object appears in the accusative case.

For the same reason as lyklana: it is a direct object, so it appears in the accusative.

• hurð = door
• hurðin = the door (nominative)
• hurðina = the door (accusative)

Since opna (to open) takes a direct object, Icelandic uses the accusative here:

• opna hurðina = open the door

Because the preposition úr (out of, from inside) requires the dative case.

So:

• vasi = pocket
• vasanum = the pocket (dative singular)

That is why Icelandic says:

• úr vasanum = out of the pocket

Many Icelandic prepositions always require a certain case, and úr is one of the ones that takes the dative.

Úr means out of or from inside.

In this sentence:

• tek lyklana úr vasanum = I take the keys out of my pocket / from the pocket

It suggests movement from inside something. That is slightly different from a more general from.

For example:

• úr vasanum = out of the pocket
• úr húsinu = out of the house

So úr is a very natural choice when something comes out of an enclosed place.

Because the same subject continues across both verbs.

So:

• Ég tek lyklana úr vasanum og opna hurðina.

means:

• I take the keys out of my pocket and open the door.

In English, we also usually do not repeat I here. Icelandic works the same way.

You could repeat it in some contexts, but normally it is unnecessary.

It actually can be a finite verb form as written: opna is both the infinitive to open and also the 1st person singular present form for this verb.

So:

• að opna = to open
• ég opna = I open / I am opening

That is why it may look unchanged, even though here it is a present-tense verb agreeing with ég.

This is common with some Icelandic verbs.

It is grammatically present tense, but like English simple present in some contexts, it can be used in a few ways depending on situation.

It could mean:

• a present action in narration: I take the keys out of my pocket and open the door
• a habitual action, depending on context
• a vivid description of events

Without more context, most learners will understand it as a straightforward present-tense statement.

If Icelandic wants to be very explicit about an action happening right now, context often does the job rather than a special verb form.

The basic structure is:

• Ég = subject
• tek = verb
• lyklana = object
• úr vasanum = prepositional phrase
• og opna hurðina = and open the door

So the sentence is basically:

Subject + Verb + Object + Prepositional phrase + and + Verb + Object

That is quite similar to English here.

It is plural.

The singular of key is:

• lykill = key

The plural is:

• lyklar = keys

And in this sentence we get the accusative definite plural:

• lyklana = the keys

So the speaker is taking more than one key.

In this sentence, Icelandic simply says úr vasanum = out of the pocket.

In many everyday situations, Icelandic does not have to state possession as explicitly as English does, especially when it is obvious from context that it is the speaker’s own pocket.

English often prefers:

• out of my pocket

But Icelandic can naturally say:

• úr vasanum

with the ownership understood from the situation.

If needed, Icelandic could make it explicit, but it often does not.

Not perfectly. A very literal version would be:

• I take the keys out of the pocket and open the door.

But natural English usually says:

• I take the keys out of my pocket and open the door.

So the Icelandic and English meanings match well, but English often adds my where Icelandic leaves possession understood.

Yes, this is a very useful sentence for spotting cases:

• Ég = nominative subject
• lyklana = accusative direct object
• vasanum = dative after úr
• hurðina = accusative direct object

So the sentence shows two very common Icelandic patterns:

1. verbs taking accusative objects
2. prepositions controlling specific cases

This is one of the big things English speakers need to get used to in Icelandic.