Hver kemur í kvöld?

Here hver is the subject of the sentence, so it is in the nominative form.

A useful thing to know is that Icelandic question words can change form depending on their grammatical role. So if who were an object instead of a subject, you would not use the same form. For example, you might see forms like hvern or hverjum in other sentences.

So in Hver kemur í kvöld?, hver is the correct form because it means who as the one doing the coming.

Kemur is the 3rd person singular present tense of the verb koma, which means to come.

So:

• koma = to come
• kemur = comes / is coming

It is singular here because hver is treated as singular in this sentence.

Because Icelandic often does not use a separate progressive form the way English does.

English makes a distinction between:

• comes
• is coming

But Icelandic very often just uses the simple present tense:

• kemur

Depending on context, kemur can mean:

• comes
• is coming
• sometimes even a near-future will come / is coming later

In this sentence, í kvöld makes the time reference clear, so kemur is naturally understood as something like is coming tonight.

This is very common in Icelandic. The present tense is often used for a planned, expected, or scheduled future event when a time expression makes the meaning clear.

So:

• Hver kemur í kvöld? literally uses present tense
• but it naturally means Who is coming tonight?

English does this too in some situations:

• Who comes tonight? is possible, though less natural in everyday speech
• Who is coming tonight? is the usual translation

So the tense form is present, but the meaning is future because of í kvöld.

Icelandic typically puts the question word first and the finite verb second.

So:

• Hver = first position
• kemur = second position

This matches a very important Icelandic pattern often called verb-second word order.

Compare:

• Hver kemur í kvöld? = Who is coming tonight?
• Kemur hann í kvöld? = Is he coming tonight?

In a yes/no question, the verb often comes first.
In a wh-question, the question word comes first, and the verb follows.

Í kvöld is a fixed time expression meaning tonight.

Even though í often corresponds to in, it is better to learn í kvöld as a whole expression rather than translating it word for word every time.

Similar Icelandic time expressions include:

• í dag = today
• í morgun = this morning
• í nótt = tonight / during the night

So in this sentence, í kvöld simply tells you when the coming happens.

Because the normal idiomatic expression is í kvöld.

Icelandic often uses a bare noun in common time expressions, without the definite article. So for the everyday meaning tonight, you normally say:

• í kvöld

not:

• í kvöldið

and not usually:

• í kvöldi

for this meaning.

So this is something best learned as a set phrase: í kvöld = tonight.

Yes, this form is singular.

If you want to make it clearly plural, Icelandic can use a plural form, for example:

• Hverjir koma í kvöld?

That would mean something like Who are coming tonight? or Which people are coming tonight?

In real conversation, context matters, but it is useful to know that Icelandic can mark this difference more clearly than English does.

You can answer either with just a name or with a full sentence.

Examples:

• Jón kemur í kvöld. = Jón is coming tonight.
• Anna og María koma í kvöld. = Anna and María are coming tonight.
• Enginn kemur í kvöld. = No one is coming tonight.

Notice that if the answer is plural, the verb changes too:

• kemur = singular
• koma = plural

In modern Icelandic, hv is usually pronounced roughly like kv.

So hver is said approximately like kver.

A few helpful pronunciation notes:

• stress in Icelandic normally falls on the first syllable
• í is a long vowel, roughly like ee
• rough English-style pronunciation guides are only approximations, but they can still help at the start

So a very rough guide to the whole sentence would begin with something like:

• kver ...

But if you are learning pronunciation seriously, it is best to listen to native audio as early as possible.