Vaktin mín byrjar klukkan sjö á morgnana.

Because -in is the suffixed definite article in Icelandic. So:

• vakt = shift
• vaktin = the shift

In this sentence, vaktin mín is the natural way to say my shift. Icelandic very often uses a definite noun plus a possessive pronoun:

• bíllinn minn = my car
• húsið mitt = my house
• vaktin mín = my shift

That is the most neutral and common word order for possession in Icelandic.

So:

• vaktin mín = my shift
  This is the normal everyday phrasing.

You can also put the possessive first in some contexts, but that usually sounds more emphatic, contrastive, or literary:

• mín vakt = my shift (with extra emphasis, like my shift, not someone else’s)

So in an ordinary statement, vaktin mín is exactly what you would expect.

Because Icelandic possessive pronouns agree with the noun in gender, number, and case.

The noun vakt is:

• feminine
• singular
• here it is the subject of the sentence, so it is in the nominative

So the correct form is mín.

Compare:

• minn for masculine singular nominative
• mín for feminine singular nominative
• mitt for neuter singular nominative

Examples:

• bíllinn minn = my car (bíll is masculine)
• vaktin mín = my shift (vakt is feminine)
• herbergið mitt = my room (herbergi is neuter)

Byrjar is the present tense, 3rd person singular form of the verb byrja, which means to begin or to start.

So:

• að byrja = to start / to begin
• byrjar = starts / begins

It is 3rd person singular because the subject is vaktin mín (my shift), which is singular.

You can think of the structure like this:

• Vaktin mín = subject
• byrjar = verb
• klukkan sjö = time
• á morgnana = habitual time expression

This is a standard Icelandic time expression. You learn it as a set pattern:

• klukkan eitt = at one o’clock
• klukkan sjö = at seven o’clock
• klukkan tíu = at ten o’clock

So klukkan + number is the normal way to give clock time.

Even though English uses at, Icelandic does not need a separate preposition here. The expression itself already functions as a time phrase.

These two expressions mean very different things:

• á morgun = tomorrow
• á morgnana = in the mornings

So in your sentence, á morgnana shows a repeated, habitual time.

Compare:

• Vaktin mín byrjar klukkan sjö á morgun. = My shift starts at seven tomorrow.
• Vaktin mín byrjar klukkan sjö á morgnana. = My shift starts at seven in the mornings.

This is a very common point of confusion for learners.

Because Icelandic often uses the plural definite form to talk about repeated times of day in a habitual sense.

So:

• á morgnana = in the mornings
• á kvöldin = in the evenings
• á næturnar = at night / during the nights

English sometimes uses a singular expression like in the morning in a general sense, but Icelandic often prefers the plural for repeated routine situations.

So á morgnana sounds natural for something that happens regularly.

It describes a routine or habitual situation.

The clue is á morgnana, which means in the mornings. That tells you this is something that happens regularly, not just once.

So the sentence gives the idea:

• My shift starts at seven in the mornings
• or more naturally in English, My shift starts at seven every morning / My morning shift starts at seven

If it were about one specific day, Icelandic would more likely use something like:

• á morgun = tomorrow
• í morgun = this morning

Yes, but Icelandic follows a strong verb-second pattern in main clauses.

The neutral order here is:

• Vaktin mín byrjar klukkan sjö á morgnana.

If you move a time phrase to the front, the verb still has to stay in second position:

• Á morgnana byrjar vaktin mín klukkan sjö.

That is also correct.

But a word order like this would not be normal in a main clause:

• Á morgnana vaktin mín byrjar ... ✗

So the sentence is a good example of normal Icelandic word order, but it also shows a pattern that can be rearranged as long as the finite verb stays in second position.

Usually, yes. Vakt commonly means a shift, especially a work shift, duty shift, or watch.

Depending on context, it can refer to things like:

• a hospital shift
• a security shift
• a night shift
• being on duty

So in this sentence, vaktin mín would normally be understood as my work shift or my duty shift.