Hann stal símanum.

Because the verb stela (to steal) takes its object in the dative case, not the accusative.

So:

• síminn = the phone (nominative)
• símann = the phone (accusative)
• símanum = the phone (dative)

Since stela governs the dative, Icelandic says:

• Hann stal símanum.

Even though in English we simply say he stole the phone, Icelandic uses dative here.

The base form is stela, meaning to steal.

Stal is the past tense singular form:

• ég stal = I stole
• þú stalst = you stole
• hann/hún/það stal = he/she/it stole

So in Hann stal símanum, stal means stole.

The ending -num shows two things at once:

1. the noun is in the dative singular
2. it is definite = the phone

The noun is sími (phone), a masculine noun.

Its singular forms are:

• sími = a phone / phone
• síma = phone (accusative/dative indefinite depending on context)
• símanum = the phone in dative
• símans = of the phone

So -num here is part of the dative singular definite form.

In Icelandic, the definite article is usually attached to the end of the noun instead of appearing as a separate word.

So:

• sími = a phone / phone
• síminn = the phone (nominative)
• símanum = the phone (dative)

That means símanum is literally something like phone-the, but in proper English we just say the phone.

Yes, that would be the indefinite version.

Compare:

• Hann stal síma. = He stole a phone.
• Hann stal símanum. = He stole the phone.

Again, the verb stela still requires the dative, so the indefinite form is síma, not nominative sími.

Yes. Hann is the masculine third-person singular pronoun meaning he.

Some related pronouns are:

• hann = he
• hún = she
• það = it

In this sentence, Hann is the subject, so it is in the nominative case.

Yes, but Icelandic still follows the verb-second pattern in main clauses.

The normal order is:

• Hann stal símanum.

But other orders are possible for emphasis or style, for example:

• Símanum stal hann.

That version emphasizes símanum more, something like It was the phone that he stole or The phone, he stole.

So the basic meaning stays the same, but the focus can shift.

No. Hann stal símanum only says that he stole the phone. It does not say from whom.

If you want to add that information, Icelandic can include another phrase, for example:

• Hann stal símanum frá henni. = He stole the phone from her.

So the sentence is complete on its own, but it leaves out the source.

A rough English-friendly guide would be:

• Hann ≈ han
• stal ≈ stahl
• símanum ≈ SEE-mah-num

A few useful notes:

• á is pronounced like the ow in now in modern Icelandic, so stal is not exactly like English stall, though stahl is a rough shortcut.
• í is like ee in see
• the stress in Icelandic is usually on the first syllable: HANN stal SEEmanum

A rough natural rhythm is: HANN stal SEE-ma-num

No. Stal is only one past-tense form of stela.

Here are some common forms:

• ég stal = I stole
• þú stalst = you stole
• hann stal = he stole
• við stálu(m)? no, the usual plural form is við stálum = we stole
• þið stáluð = you (plural) stole
• þeir/þær/þau stálu = they stole

So stal is specifically the singular form used with he/she/it and also I.

Icelandic verbs usually carry tense themselves, so there is no helper verb like English do/did in ordinary past statements.

English:

• He stole the phone.
• Did he steal the phone?
• He did not steal the phone.

Icelandic uses the main verb directly instead:

• Hann stal símanum.
• Stal hann símanum?
• Hann stal ekki símanum.

So the tense is already built into stal.