Hún syngur best á kvöldin.

A word-for-word breakdown is:

• Hún = she
• syngur = sings
• best = best
• á kvöldin = in the evenings / at night

So the full sentence means something like She sings best in the evenings.

A more literal translation of á kvöldin might look odd in English, because Icelandic uses this expression idiomatically for time.

Syngur is the correct finite verb form for hún (she) in the present tense.

The verb is að syngja = to sing.

Its present-tense forms include:

• ég syng = I sing
• þú syngur = you sing
• hún syngur = she sings
• við syngjum = we sing

So in this sentence, hún syngur means she sings.

Syngja is the infinitive form, meaning to sing, so you would not use that directly after hún here.

Here best is an adverb, because it describes how she sings, not what she is like.

A useful comparison is:

• vel = well
• betur = better
• best = best

So:

• Hún syngur vel. = She sings well.
• Hún syngur betur. = She sings better.
• Hún syngur best. = She sings best.

This is similar to English well → better → best, except Icelandic uses the forms vel → betur → best.

This is a very common thing learners notice. Icelandic á often does mean on, but with time expressions it can correspond to English in or at.

So:

• á morgnana = in the mornings
• á kvöldin = in the evenings
• á nóttunni = at night

In other words, you should learn á kvöldin as a natural time expression, not translate á too literally here.

Yes. The -in is the suffixed definite article, so kvöldin is the definite form.

But in this expression, the whole phrase á kvöldin is best understood as an idiomatic time phrase meaning:

• in the evenings
• during the evenings
• in the evening, as a habit

So even though the form is definite, the natural English translation is usually not something like on the evenings, but in the evenings.

Because á kvöldin usually expresses a repeated or habitual time: in the evenings, evenings in general, at night regularly.

So:

• Hún syngur best á kvöldin. = She sings best in the evenings.

This gives a general pattern, not just one specific evening.

If you wanted a more specific time expression, Icelandic would often use a different phrase.

This is an important distinction:

• á kvöldin = in the evenings, habitually, in general
• í kvöld = tonight, one specific evening

So:

• Hún syngur best á kvöldin. = She sings best in the evenings.
• Hún syngur í kvöld. = She is singing tonight / She sings tonight.

A learner should be careful not to confuse these, because the meanings are quite different.

The sentence is following a very natural Icelandic word order:

• subject: Hún
• verb: syngur
• adverb: best
• time phrase: á kvöldin

So the structure is:

She + sings + best + in the evenings

This is the most straightforward way to say it.

You might see different word orders in Icelandic for emphasis, but Hún syngur best á kvöldin is the neutral, standard phrasing.

Yes, that is very close in meaning.

Depending on context, á kvöldin can be translated as:

• in the evenings
• at night
• in the evening

The most natural translation here is usually in the evenings, because the Icelandic phrase suggests a repeated habit or general tendency.

So the idea is not necessarily one single performance, but rather that evening is the time when she sings best.

A rough pronunciation guide for an English speaker is:

• Hún ≈ hoon
• syngur ≈ something like SIN-gur or SING-gur, but with an Icelandic y sound that does not match English exactly
• best = almost like English best
• á = ow as in cow, but longer
• kvöldin ≈ KVOL-tin or KVOL-din, depending on how narrowly you describe the sounds

A few helpful notes:

• ú in Hún is a long vowel.
• y in syngur is not exactly the English i or u.
• ö in kvöldin is also a vowel English does not have exactly.

If you are learning pronunciation, it is best to hear this from a native speaker or audio resource, because Icelandic vowels can be hard to guess from English spelling habits.

Normally, yes, hún is needed here.

Icelandic usually keeps the subject pronoun unless there is some special context where it is already understood and omitted in less standard or very informal language. In ordinary correct Icelandic, you would say:

• Hún syngur best á kvöldin.

So unlike Spanish or Italian, Icelandic does not regularly drop subject pronouns in normal sentences.

Yes: it belongs to an irregular comparison pattern.

Instead of something fully predictable, you should memorize:

• vel = well
• betur = better
• best = best

That is very useful because these forms are common. So when you see syngur best, you should immediately think sings best, not try to build it from an adjective form.