Hún athugar inneignina sína í netbankanum á hverjum föstudegi.

In a normal declarative sentence, Icelandic usually includes the subject, so hún means she and is not normally omitted here.

So:

• Hún athugar ... = She checks ...

Icelandic is not like Spanish or Italian, where the subject pronoun is often left out because the verb ending already shows who is doing the action. Icelandic verb forms do not usually make the subject clear enough on their own, so pronouns are commonly stated.

Athugar is the present tense of the verb að athuga, which often means:

• to check
• to examine
• to look into
• to inspect

In this sentence, athugar is best understood as checks.

Grammatically:

• að athuga = infinitive, to check
• athugar = present tense, checks

So Hún athugar ... literally means She checks ...

Because inneignina is the definite form: the balance / the credit rather than just balance / credit.

Here is the breakdown:

• inneign = balance, credit (indefinite)
• inneignin = the balance (nominative definite)
• inneignina = the balance in the accusative definite

It appears in the accusative because að athuga takes a direct object, and the direct object here is inneignina sína = her balance.

So:

• Hún athugar inneign. = She checks a balance / balance.
• Hún athugar inneignina. = She checks the balance.

That -a shows the accusative singular definite form of the noun.

The noun inneign is feminine. In this sentence it is:

• singular
• definite
• direct object of the verb

That combination gives inneignina.

A learner does not need to memorize every full declension immediately, but the important point is:

• the verb athugar needs a direct object
• that object appears here in the accusative
• so the definite form becomes inneignina

Because sína is the reflexive possessive, used when the possessor is the same as the subject of the sentence.

Here, the subject is hún = she, and the thing possessed is inneignina = the balance. Since it is her own balance, Icelandic uses sína.

So:

• Hún athugar inneignina sína. = She checks her own balance.
• Hún athugar inneignina hennar. = She checks her balance, where her usually refers to some other female person, not the subject.

This is a very important Icelandic distinction.

Because sinn changes form to match the noun it belongs to.

It agrees with inneignina, which is:

• feminine
• singular
• accusative

That gives:

• sína

So the form is not chosen based on the subject’s gender alone. It is chosen based on the noun being possessed.

Very roughly:

• masculine accusative singular: sinn
• feminine accusative singular: sína
• neuter accusative singular: sitt

Here the possessed noun is inneignina, a feminine noun, so sína is the correct form.

Í netbankanum means in the online bank or more naturally in the online banking app/system.

Breakdown:

• í = in
• netbanki = online bank / online banking system
• netbankanum = the online bank in the dative singular definite

The preposition í can take either:

• dative for location: in
• accusative for motion into something: into

Here there is no movement. She is checking her balance in the online bank, so Icelandic uses the dative:

• í netbankanum

Compare:

• Hún er í bankanum. = She is in the bank.
• Hún fer í bankann. = She goes into the bank.

That ending is part of the dative singular definite form of the masculine noun netbanki.

So:

• netbanki = online bank
• netbankann = the online bank, accusative definite
• netbankanum = the online bank, dative definite

Because í here expresses location, it requires the dative, which gives netbankanum.

That is a common Icelandic way to express repeated time: literally on each Friday.

Breakdown:

• á = on
• hverjum = each / every, dative singular
• föstudegi = Friday, dative singular

So the whole phrase literally means:

• on each Friday

but in natural English that is usually just:

• every Friday

Because the preposition á here takes the dative in this time expression.

So both words appear in the dative singular masculine:

• hver dagur type word changes to hverjum in dative
• föstudagur changes to föstudegi in dative

This is normal agreement:

• the adjective/pronoun hverjum matches the noun
• the noun föstudegi is also in dative because of á

Föstudagur is the dictionary form, usually the nominative singular: Friday.

But after á in this expression, the noun must be in the dative singular, which is:

• föstudegi

So:

• föstudagur = Friday
• á föstudegi = on Friday
• á hverjum föstudegi = every Friday

Many Icelandic masculine nouns change from -ur in the nominative to -i in the dative singular.

No, this is a very normal Icelandic sentence order.

Structure:

• Hún = subject
• athugar = verb
• inneignina sína = object
• í netbankanum = place/method phrase
• á hverjum föstudegi = time phrase

So the sentence follows a very natural pattern:

Subject + Verb + Object + other information

Icelandic word order can be flexible, but this version is straightforward and neutral.

Yes. Icelandic allows a good deal of flexibility, especially with adverbials such as time and place.

For example, you could also say:

• Á hverjum föstudegi athugar hún inneignina sína í netbankanum.

That gives more emphasis to every Friday.

But the original sentence is completely natural and probably the most neutral way to say it.

Yes, quite often. Netbanki refers to an online banking system, web banking service, or banking interface.

So í netbankanum does not necessarily mean a physical bank. It usually means something like:

• in her online banking account
• in the online banking system
• in the banking app/site

English often says in online banking, in the banking app, or simply online, while Icelandic comfortably uses í netbankanum.

Normally, no. Icelandic does not capitalize days of the week unless they begin a sentence.

So:

• föstudagur = Friday
• á hverjum föstudegi = every Friday

This is different from English, where Friday is capitalized.

Probably these three:

1. Reflexive possession

   • sína means her own
   • not the same as hennar

2. Prepositions and case

   • í netbankanum uses dative because it shows location
   • á hverjum föstudegi also uses dative in this time expression

3. Case on the direct object

   • inneignina is in the accusative because it is the object of athugar

So this one sentence is a very good example of how Icelandic combines:

• verb + object case
• reflexive possessives
• prepositions controlling case