Á kvöldin rugga ég henni í smástund, og þá sofnar hún fljótt.

Á kvöldin means in the evenings.

It is plural because the sentence describes something that happens repeatedly, as a habit, not just on one single evening. Icelandic often uses this kind of time expression for regular routines:

• á morgnana = in the mornings
• á kvöldin = in the evenings

So the plural gives the sense of whenever evening comes / evening after evening.

For habitual time expressions, Icelandic very often uses forms like á kvöldin, á morgnana, á næturnar, and so on. This is the normal idiomatic way to say in the evenings, in the mornings, etc.

Á kvöldunum is possible in some contexts, but it sounds more specific, like referring to particular evenings already known from the context. For a general routine, á kvöldin is the natural choice.

This is because Icelandic follows the verb-second rule in main clauses.

When a sentence starts with something other than the subject, the finite verb usually comes next. Here the first element is Á kvöldin, so the verb rugga comes second, and the subject ég comes after it:

• Á kvöldin = first element
• rugga = finite verb, second position
• ég = subject

So:

• Ég rugga henni í smástund. = neutral order
• Á kvöldin rugga ég henni í smástund. = time expression moved to the front

The same thing happens later in þá sofnar hún fljótt.

In the present tense, many Icelandic verbs do not have a special ending for ég. The 1st person singular often looks the same as the infinitive stem.

With að rugga:

• ég rugga = I rock
• þú ruggar = you rock
• hún ruggar = she rocks

So rugga is the correct present-tense form for ég.

Að rugga means to rock, to sway, or to gently move back and forth.

In this sentence, it means rocking someone gently, probably to help them fall asleep.

A very important point is that rugga takes a dative object, which is why the pronoun is henni and not hana.

Henni is the dative singular form of hún.

The verb rugga takes its object in the dative, so you get:

• ég rugga henni = I rock her

This is something learners often just have to memorize with the verb:

• rugga einhverjum = rock someone

If the verb took the accusative, you would expect hana, but here Icelandic requires henni.

Í smástund means for a little while or for a short while.

Here í is used in a time expression showing duration. In Icelandic, í + accusative is often used to mean for a certain length of time:

• í eina klukkustund = for one hour
• í smástund = for a little while

So this does not mean movement into something. It is a time phrase meaning duration.

Also, smástund is basically a noun meaning a short while / little while.

Here þá means something like then, at that point, or when that happens.

So the idea is:

• I rock her for a little while,
• then she falls asleep quickly.

It connects the second clause to the first and shows the result or next step.

It also triggers normal verb-second order:

• þá sofnar hún fljótt

not

• þá hún sofnar fljótt

Sofnar is from the verb að sofna, which means to fall asleep.

This is different from að sofa, which means to sleep or to be asleep.

So:

• hún sefur = she is sleeping / she sleeps
• hún sofnar = she falls asleep

In this sentence, sofnar is the right choice because it describes the moment or process of going to sleep, not the state of already being asleep.

No, not here. Hún has to be there.

The first clause has the subject ég, but the second clause has a different subject: hún. Since Icelandic normally does not drop subject pronouns the way some languages do, the second clause needs its own explicit subject:

• ... og þá sofnar hún fljótt.

Without hún, the clause would be incomplete.

Because Icelandic, like English, often uses the present tense for habitual actions.

So the present tense here means something like:

• In the evenings, I rock her for a little while, and then she falls asleep quickly.

This is not necessarily happening right now. It can describe a repeated routine or general pattern.

Here fljótt is an adverb, because it modifies the verb sofnar:

• sofnar fljótt = falls asleep quickly

It tells you how she falls asleep.

The form fljótt is also identical to the neuter singular form of the adjective fljótur, but in this sentence it is functioning as an adverb, so the meaning is quickly, not quick.