Questions & Answers about 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.