Learn Hardcore Icelandic: Ég veit ekki hvort hún kemur í kvöld. - I do not know whether she is coming tonight.

Ég – I (1st person singular, nominative)
veit – know (1st person singular present of vita, to know)
ekki – not
hvort – whether / if (introduces an indirect yes/no question)
hún – she (3rd person singular, nominative)
kemur – comes / is coming (3rd person singular present of koma, to come)
í – in
kvöld – evening, here: tonight / this evening

So the structure is literally: I know not whether she comes tonight.

Why is the word order veit ekki and not ekki veit, like “I not know”?

In Icelandic main clauses, the finite verb normally comes in second position (the so‑called V2 rule).
Here, the finite verb is veit, so it must come right after the subject Ég:

Ég veit ekki … = I know not …

Putting ekki before the verb (Ég ekki veit …) would break this rule and is ungrammatical in normal word order. The negation ekki typically comes right after the conjugated verb in simple statements.

What exactly does hvort mean here, and how is it different from ef?

In this sentence, hvort means whether (also often translated as if in English). It introduces an indirect yes/no question – something you could ask as a direct question:

Direct: Kemur hún í kvöld? – Is she coming tonight?
Indirect: Ég veit ekki hvort hún kemur í kvöld. – I don’t know whether she is coming tonight.

ef is mainly the conditional “if” (If X happens, Y will happen):

Ef hún kemur í kvöld, verður gaman. – If she comes tonight, it will be fun.

You would not say Ég veit ekki ef hún kemur í kvöld; that sounds wrong in standard Icelandic. For “I don’t know if/whether…”, you want hvort.

Why is kemur in the present tense when English would often use “will come” or “is coming”?

Icelandic often uses the present tense for future events when the context makes the time clear, especially with time expressions like í kvöld, á morgun, næsta ár etc.

So hún kemur í kvöld literally is she comes tonight, but it naturally means she is coming / will come tonight.
There is a future auxiliary mun (hún mun koma í kvöld), but it is not required; the simple present is very common for planned or expected future events.

Can you leave out hvort, like in English “I don’t know she’s coming tonight”?

No. In Icelandic you must have some kind of conjunction or particle to introduce the subordinate clause here.

Correct: Ég veit ekki hvort hún kemur í kvöld.
Incorrect: *Ég veit ekki hún kemur í kvöld.

You also cannot simply replace hvort with að here; Ég veit ekki að hún komi í kvöld would mean something more like I am not aware that she is coming tonight, which is a different nuance.

Why is it hún and not henni or some other form of “she”?

hún is the nominative form and is used for the subject of the verb kemur:

hún kemur – she comes / is coming.

henni is the dative form, used when “her” is an indirect object:

Ég gef henni bók. – I give her a book.

Since “she” is the one doing the action of coming in this clause, it must be hún, not henni or any other form.

What case is kvöld in after í, and why is there no article like “the” in Icelandic?

In í kvöld, the noun kvöld is effectively in the accusative singular, but because kvöld is a neuter noun with the same form in nominative and accusative, it just looks like the dictionary form.

Time expressions like í kvöld, í gær, í fyrra often appear without an article, and the whole phrase works like an adverb meaning tonight. Icelandic time expressions commonly omit articles where English would use the or no article at all.

Is the word order inside the hvort‑clause always “subject–verb” like hún kemur?

Yes, in subordinate clauses (like those starting with hvort, að, þegar, ef etc.), Icelandic typically uses subject–verb–object word order, without the V2 rule.

So you say:

hvort hún kemur í kvöld – whether she comes tonight

and not:

*hvort kemur hún í kvöld in this indirect context.

Kemur hún í kvöld? is fine as a direct question, but once you embed it under ég veit ekki hvort…, you switch to the normal subordinate clause order hún kemur.

Can you also say Ég veit ekki hvort hún komi í kvöld? What is the difference between kemur and komi?

Yes, Ég veit ekki hvort hún komi í kvöld is also grammatically correct.

kemur is present indicative: neutral, everyday form.
komi is present subjunctive: it can give a slightly stronger feeling of uncertainty, and often sounds more formal or literary.

In modern spoken Icelandic, many people just use the indicative (kemur) in sentences like this, but you will still see and hear the subjunctive (komi) in more careful or formal language.

What is the difference between í kvöld, í nótt, and í dag? When should I use í kvöld?

Roughly:

í kvöld – this evening / tonight (the evening part of today, before you go to bed)
í nótt – tonight / last night, but referring to the nighttime (when people are normally sleeping)
í dag – today (during the day)

So Ég veit ekki hvort hún kemur í kvöld means you are unsure whether she will come this evening, not in the late night or earlier in the day.

How do you pronounce hvort and kvöld? They look tricky.

Very roughly in English-friendly terms:

hvort: often pronounced close to “kvort” with a puff of air on the k. More precisely something like [kʰvɔr̥t] – short o (like in “pot” for many speakers), and the rt is a tight cluster.
kvöld: roughly like “kveult”. More precisely [kʰvœlt] – the vowel [œ] is like the German ö, and the final ld is pronounced together, with the d often quite weak.

Icelandic spelling preserves old patterns, so the pronunciation isn’t always obvious from the letters; listening to native audio for words like hvort and kvöld is very helpful.