Ég veit ekki hvaða kjól ég á að velja í kvöld.

Hvaða is the Icelandic word for which/what kind of when it comes before a noun. In modern Icelandic, hvaða is generally indeclinable, which means it usually stays the same instead of changing for gender, number, or case.

So in:

hvaða kjól = which dress

the noun changes form as needed, but hvaða stays hvaða.

That is very convenient for learners, because you do not have to memorize a whole set of forms for hvaða in everyday use.

The dictionary form is kjóll = dress.

But in the sentence, it appears as kjól, because it is in the accusative singular:

• nominative: kjóll
• accusative: kjól

This happens because velja (to choose) takes a direct object, and that object is commonly in the accusative.

So:

• kjóll = a dress, as subject
• ég vel kjól = I choose a dress

The pattern eiga að + infinitive is a very common Icelandic construction. It often means:

• to be supposed to
• to should
• to have to, depending on context

So:

• ég á að velja literally means something like I am supposed to choose
• in natural English here, it can come out as I should choose or I’m supposed to choose

In this sentence, it does not mean ownership, even though eiga by itself often means to own / to have.

Compare:

• Ég á bíl. = I own / have a car.
• Ég á að fara. = I am supposed to go.

So learners need to recognize á að as a set expression here.

Because ég vel means I choose / I am choosing, while ég á að velja adds the idea of what I should choose or what I’m supposed to choose.

The sentence is not simply about the act of choosing. It is about uncertainty regarding the right or intended choice.

So these are different:

• Ég veit ekki hvaða kjól ég vel.
  This sounds more like I don’t know which dress I’m choosing and is less natural in this context.

• Ég veit ekki hvaða kjól ég á að velja.
  I don’t know which dress I should choose.

The second is the natural one when someone is trying to decide.

Because this is an embedded question after Ég veit ekki.

In a main question, Icelandic often has verb-second/inversion word order:

• Hvaða kjól á ég að velja?
  = Which dress should I choose?

But when that question is embedded inside another sentence, the word order changes:

• Ég veit ekki hvaða kjól ég á að velja.
  = I don’t know which dress I should choose.

So:

• Hvaða kjól á ég að velja? = direct question
• ... hvaða kjól ég á að velja = indirect/embedded question

This is similar to English:

• Which dress should I choose?
• I don’t know which dress I should choose.

Icelandic mainly distinguishes between:

• vita = to know a fact, answer, piece of information
• þekkja = to know / be acquainted with a person, place, or something familiar

Here, the speaker says I don’t know which dress..., meaning I do not know the answer / I am uncertain. That requires vita.

So:

• Ég veit ekki... = I don’t know...
• Ég þekki hana. = I know her.

A native English speaker often has to learn this split, because English uses know for both ideas.

Í kvöld is a fixed expression meaning tonight.

Literally, it is something like in evening / this evening, but as a whole it functions as an adverbial time phrase.

You normally just learn it as a set expression:

• í morgun = this morning
• í dag = today
• í kvöld = tonight

There is no article because this expression is idiomatic as it is. You should think of í kvöld as one chunk rather than trying to build it word by word every time.

Yes. Kjóll is the standard Icelandic word for a dress.

Its forms include:

• nominative singular: kjóll
• accusative singular: kjól
• dative singular: kjól
• genitive singular: kjóls

It is a masculine noun, which can feel surprising to English speakers, because grammatical gender does not have to match natural gender or the typical wearer of the item.

So even though a dress is commonly associated with women’s clothing, the word kjóll is grammatically masculine.

Yes, and the nuance changes slightly.

• ég á að velja often means I am supposed to choose / I should choose
• ég ætti að velja means more like I ought to choose / I should probably choose

So:

• Ég veit ekki hvaða kjól ég á að velja í kvöld.
  = I don’t know which dress I’m supposed to choose / should choose tonight.

• Ég veit ekki hvaða kjól ég ætti að velja í kvöld.
  = I don’t know which dress I ought to choose tonight.

The version with á að can sound a bit stronger or more obligation-based, while ætti að is often softer and more like advice or personal judgment.

It would be:

Hvaða kjól á ég að velja í kvöld?

That means:

Which dress should I choose tonight?

Notice the word order difference:

• direct question: Hvaða kjól á ég að velja...?
• embedded question: ... hvaða kjól ég á að velja

This is a very useful pair to learn together.

A rough learner-friendly pronunciation is:

yehg vait ehk-ih khvai-tha kyoul yehg ow ath vehl-ya ee kvuhld

A few notes:

• Ég begins with a y-like sound.
• ei in veit sounds roughly like ay in day.
• ð in hvaða is often like a soft th in this.
• kj in kjól is a palatal sound that English does not have exactly; learners often approximate it with ky at first.
• á sounds like ow.
• kvöld has a rounded vowel and a consonant cluster that may take practice.

It is completely normal if this sentence feels difficult to pronounce at first. Icelandic sound combinations often need repeated listening and imitation.