Hann var pirraður af því að hann fann ekki hringinn sinn áður en þau fóru út.

Pirraður agrees with hann.

Here, hann is:

• masculine
• singular
• nominative

So the adjective also appears in the masculine singular nominative form: pirraður.

You can think of hann var pirraður as meaning he was annoyed, where the adjective has to match he grammatically.

For comparison:

• hann var pirraður = he was annoyed
• hún var pirruð = she was annoyed
• það var pirrað = it was annoyed

Af því að means because.

So:

• Hann var pirraður af því að... = He was annoyed because...

This is a very common way to introduce a reason in Icelandic.

You may also see other expressions for because, such as:

• því að
• vegna þess að

But in this sentence, af því að is a normal and natural choice.

The second hann is the subject of the subordinate clause.

The sentence has two parts:

1. Hann var pirraður = He was annoyed
2. af því að hann fann ekki hringinn sinn... = because he did not find his ring...

Even though English also repeats he here, learners sometimes wonder whether Icelandic could leave it out. In this kind of sentence, it normally stays explicit:

• af því að hann fann... = because he found...
• af því að hann fann ekki... = because he did not find...

Fann is the past tense of finna, which means to find.

So:

• finna = to find
• finnur = finds / is finding
• fann = found

In the sentence:

• hann fann ekki hringinn sinn = he did not find his ring

This is an irregular verb, so the past tense is not formed in a simple predictable way from the infinitive.

In this sentence, ekki negates the verb phrase:

• hann fann ekki hringinn sinn = he did not find his ring

This placement is very common in Icelandic:

• subject + verb + ekki
  • object

So:

• hann fann ekki... not
• hann ekki fann...

A good basic pattern to remember is:

• Ég sá ekki bílinn. = I did not see the car.
• Við komum ekki í dag. = We are not coming today / We did not come today, depending on context.

Hringinn is the accusative singular definite form of hringur (ring).

That happens because it is the direct object of fann:

• hann fann hringinn = he found the ring

The dictionary form is:

• hringur = ring

But the sentence needs:

• hringinn = the ring

So this shows both:

• case: accusative
• definiteness: the ring, not just a ring

Sinn is a reflexive possessive. It is used when the possessor is the same as the subject of the clause.

Here:

• hann fann ekki hringinn sinn = he did not find his own ring

The subject of the clause is hann, and the ring belongs to that same person, so sinn is the correct choice.

Compare:

• Hann fann ekki hringinn sinn. = He did not find his own ring.
• Hann fann ekki hringinn hans. = He did not find his ring, meaning someone else’s ring.

This distinction is very important in Icelandic.

Like adjectives, sinn changes form to agree with the noun it goes with.

It agrees with hringinn, which is:

• masculine
• singular
• accusative

So the correct form is:

• sinn

Compare some other forms:

• bókina sína = his/her own book
  (bókina is feminine accusative singular)
• barnið sitt = his/her own child
  (barnið is neuter accusative/nominative singular)
• hringinn sinn = his own ring
  (masculine accusative singular)

Áður en means before when it introduces a clause.

In this sentence:

• áður en þau fóru út = before they went out

So the structure is:

• áður en
  • clause

Examples:

• Áður en ég fór = before I went
• Áður en við borðuðum = before we ate

It is not just a single-word preposition here; it introduces a full clause with its own subject and verb.

Þau is the neuter plural form of they.

It is often used:

• for a mixed-gender group
• for a group where gender is not being specified
• for certain natural group references, depending on context

So:

• þau fóru út = they went out

The singular forms are:

• hann = he
• hún = she
• það = it

And plural:

• þeir = they (masculine)
• þær = they (feminine)
• þau = they (neuter / mixed / unspecified in many contexts)

Because its subject is þau, which is plural.

The verb fara means to go, and its past tense changes depending on the subject.

Here:

• þau fóru út = they went out

Compare:

• ég fór = I went
• hann fór = he went
• hún fór = she went
• þau fóru = they went

So fóru is the plural past form.

Út means out.

So:

• fóru út = went out

This is a very common verb + adverb combination in Icelandic, similar to English phrasal-style expressions:

• fara út = go out
• koma inn = come in
• fara heim = go home

In this sentence, út tells you the direction or movement: they went outside / went out.

Yes, Icelandic word order is somewhat flexible, but this sentence uses a very neutral, natural order.

Basic structure:

• Hann var pirraður
• af því að hann fann ekki hringinn sinn
• áður en þau fóru út

This gives:

1. the main statement
2. the reason
3. the time frame

You could move some parts for emphasis, but the original is straightforward and easy to process.

For example, Icelandic often allows fronting:

• Áður en þau fóru út fann hann ekki hringinn sinn.
• Af því að hann fann ekki hringinn sinn var hann pirraður.

Those are possible, but the original sentence sounds like a normal unmarked way to say it.

It means was annoyed, not specifically became annoyed.

• vera pirraður = to be annoyed
• verða pirraður = to become annoyed / get annoyed

So:

• Hann var pirraður = He was annoyed
• Hann varð pirraður = He got annoyed / became annoyed

In your sentence, the focus is on his state, and the reason for that state is then explained.

Yes. In everyday speech, people may pronounce it quickly, and in casual language you may notice variation in how strongly each part is pronounced.

In writing, though, af því að is the standard full form.

Learners should generally use the full written form until they are comfortable with colloquial speech patterns. It is the safest and clearest choice.