Jeg ved ikke præcist, hvornår bussen kommer.

A word-by-word breakdown is:

• Jeg = I
• ved = know
• ikke = not
• præcist = exactly / precisely
• hvornår = when
• bussen = the bus
• kommer = comes / is coming / will come

So the whole sentence means something like I don’t know exactly when the bus is coming.

Yes, this is the know used for facts or information.

In Danish:

• at vide / ved = to know a fact, piece of information, or answer
• at kende = to know a person, place, or be familiar with something

So Jeg ved ikke ... means I don’t know ... in the sense of not knowing information.

Examples:

• Jeg ved det. = I know it / I know that.
• Jeg kender ham. = I know him.

Because Danish main clauses usually follow the V2 rule: the finite verb comes early, typically in second position.

So in a normal statement:

• Jeg ved ikke ...

Here:

• Jeg = subject
• ved = finite verb
• ikke = negation

This is the normal main-clause order in Danish.

English speakers sometimes expect the negation to behave differently, but in Danish ikke usually comes after the finite verb in a main clause.

Because ikke is negating the idea know exactly.

So:

• Jeg ved ikke præcist ... = I do not know exactly ...

This sounds natural in Danish and means the speaker may know something roughly, but not with precision.

If you remove præcist, the sentence becomes:

• Jeg ved ikke, hvornår bussen kommer.
• I don’t know when the bus is coming.

Adding præcist gives the sense of not exactly or not precisely.

Because hvornår bussen kommer is a subordinate clause.

Danish normally uses a comma before subordinate clauses much more consistently than English does. So:

• Jeg ved ikke præcist, hvornår bussen kommer.

The part after the comma functions like when the bus comes / is coming.

Because this is an embedded question (also called an indirect question), not a direct question.

Direct question:

• Hvornår kommer bussen? = When is the bus coming?

Embedded question:

• Jeg ved ikke præcist, hvornår bussen kommer. = I don’t know exactly when the bus is coming.

In Danish, embedded questions usually have subordinate-clause word order, so the subject comes before the verb:

• hvornår bussen kommer

not

• hvornår kommer bussen

This is similar to English:

• direct: When is the bus coming?
• embedded: I don’t know when the bus is coming.

Hvornår means when? in questions or indirect questions.

Examples:

• Hvornår kommer bussen? = When is the bus coming?
• Jeg ved ikke, hvornår bussen kommer. = I don’t know when the bus is coming.

Når is usually used more like when in the sense of whenever / when at the time that in statements, not as a question word.

Example:

• Når bussen kommer, går vi ombord.
• When the bus comes, we get on.

So in your sentence, hvornår is correct because the speaker does not know the time.

Because bussen means the bus, with the definite article attached to the end of the noun.

In Danish, definiteness is often shown with a suffix:

• en bus = a bus
• bussen = the bus

So bussen refers to a specific bus, probably the one both speaker and listener already know about.

Because Danish, like English, often uses the present tense for scheduled future events.

So:

• bussen kommer literally = the bus comes
• but naturally it means the bus is coming or the bus will come

This is especially common with timetables, transport, and planned events.

Examples:

• Toget kører klokken otte. = The train leaves at eight.
• Bussen kommer snart. = The bus is coming soon.

Yes. If you remove it, the sentence is still completely natural:

• Jeg ved ikke, hvornår bussen kommer.

That simply means I don’t know when the bus is coming.

Adding præcist makes it slightly more specific:

• maybe you know roughly
• but you do not know the exact time

Sometimes yes, but the nuance may change slightly.

The most natural version here is:

• Jeg ved ikke præcist, hvornår bussen kommer.

You may also hear:

• Jeg ved ikke, hvornår bussen præcist kommer.

That version puts more focus on the exact timing of the bus’s arrival. It is understandable, but often sounds a bit more marked or formal.

For most learners, Jeg ved ikke præcist, hvornår bussen kommer is the safest and most natural choice.

The direct-question version would be:

• Hvornår kommer bussen?

That means When is the bus coming?

Notice the word order difference:

• direct question: Hvornår kommer bussen?
• embedded question: ... hvornår bussen kommer

This is one of the most important patterns to learn in Danish.

The spelling is historical. In modern Danish, the h in hvornår is not pronounced separately the way an English speaker might expect.

So hvornår is pronounced roughly like vor-nor or vo-nor, depending on accent and speed, not like h-vor-nor.

Many Danish words beginning with hv- behave similarly, for example:

• hvad
• hvem
• hvor

The spelling stays traditional, but the pronunciation is simpler than it looks.

Yes, very common.

The pattern is:

• Jeg ved ikke ... = I don’t know ...
• followed by an embedded question:
  • hvor = where
  • hvornår = when
  • hvem = who
  • hvordan = how
  • om = whether/if

Examples:

• Jeg ved ikke, hvor han bor. = I don’t know where he lives.
• Jeg ved ikke, hvem det er. = I don’t know who it is.
• Jeg ved ikke, om hun kommer. = I don’t know whether she is coming.

So your sentence is an excellent example of a very useful everyday structure.