Sökin er mín.

Because -in is the suffixed definite article in Icelandic.

The basic noun is sök = fault / blame / guilt.
So:

• sök = fault
• sökin = the fault

Unlike English, Icelandic very often puts the definite article onto the end of the noun instead of using a separate word like the.

The dictionary form is sök.

In this sentence, it appears as sökin, which is the nominative singular definite form.

So if you look it up in a dictionary, you would search for sök, not sökin.

Because mín has to agree with the noun sök in gender, number, and case.

The noun sök is:

• feminine
• singular
• nominative here

So the correct possessive form is mín.

Compare:

• minn = masculine
• mín = feminine
• mitt = neuter

Since sök is feminine, mín is the right form.

Because here mín means mine, not my.

This sentence is built like:

• Sökin = the fault
• er = is
• mín = mine

So the structure is literally The fault is mine.

If you put the possessive before the noun, you get a noun phrase instead:

• mín sök = my fault

That is not a full sentence by itself.
So:

• mín sök = my fault
• Sökin er mín = The fault is mine / It is my fault

Both sökin and mín are in the nominative.

That is because sökin is the subject, and after vera (to be), the complement is also usually nominative in Icelandic.

So:

• sökin = nominative singular definite
• mín = nominative singular feminine

This is very similar to older or more formal English patterns like It is I, where the form after is is still linked to the subject.

Er is the 3rd person singular present tense of vera, the verb to be.

So here it simply means is.

A few common forms of vera are:

• ég er = I am
• þú ert = you are
• hann / hún / það er = he / she / it is

So Sökin er mín literally has the same basic verb structure as The fault is mine.

Yes. It is correct and natural.

It can sound a little more like The blame is mine or The fault is mine, so it may feel slightly more formal, emphatic, or weighty than casual everyday English It’s my fault.

A very common everyday Icelandic expression is also:

Þetta er mér að kenna
Literally: This is for me to answer for / blame belongs to me
Idiomatic meaning: It’s my fault

So Sökin er mín is good Icelandic, but depending on context, Icelandic speakers may also use other expressions.

Yes, you can.

Þetta er mín sök also means It is my fault.

The difference is mainly in structure and emphasis:

• Þetta er mín sök = This/it is my fault
• Sökin er mín = The fault is mine

The second one puts more focus on who the fault belongs to. It can sound a bit more emphatic or contrastive.

In normal, neutral usage, Sökin er mín is the standard order.

Icelandic does allow other word orders for emphasis, style, or poetic effect, but changing the order usually makes the sentence sound marked rather than neutral.

So for a learner, the safest version to use is:

Sökin er mín.

A rough guide is:

SÖ-kin er meen

A few helpful notes:

• ö is not like English o. It is closer to German ö or French eu.
• í in mín is a long ee sound.
• The r in er is an Icelandic r, not an English-style r.

So the hardest part for most English speakers is usually the vowel in sökin.

It can, yes.

Because Icelandic is saying The fault is mine, it can feel a bit stronger than a plain casual admission. It may suggest something like:

• I take the blame
• The responsibility is mine
• It’s my fault, not someone else’s

Whether it sounds strongly emphatic depends on the context and intonation, but the structure naturally gives a slight sense of emphasis or ownership.