Learn Hardcore Norwegian: Det er ingen buss i dag.

In Norwegian, existential statements (“there is/are”) usually use the dummy subject Det er (literally “It is”). Without Det er, Ingen buss i dag sounds like a fragment or a headline. Adding Det er makes it a full sentence: “There is no bus today.”

What exactly does ingen mean here? How is it different from ikke + noe?

Ingen is a negative indefinite adjective placed directly before a noun, meaning “no” or “not any.”
– You say ingen buss (“no bus”).
Ikke is a negating adverb and needs a pronoun like noe (“something”) if you want “not any.” That construction usually replaces a clause, e.g. Jeg har ikke noe busskort (“I don’t have any bus ticket”), but you wouldn’t say Det er ikke noe buss to mean “there is no bus.”

Why is there no article before buss? Shouldn’t it be en buss?

Because ingen already negates and expresses indefiniteness, you drop any article. If you said en buss, it would mean “one bus,” which clashes with ingen (“no bus”). So the form is simply ingen buss.

Could I move i dag to the front? For example: I dag er det ingen buss?

Yes. Time adverbials like i dag can go first. That triggers subject–verb inversion:
“I dag er det ingen buss.”
Here er (verb) comes before det (subject), which is perfectly natural in Norwegian.

Is buss masculine or feminine? Why isn’t it ei buss?

In Bokmål, buss is a masculine noun, so its indefinite form is en buss and definite is bussen. You don’t use ei (feminine article) here. When negated by ingen, the article (en) simply disappears.

Can I use finnes instead of er? Like Det finnes ingen buss i dag?

Yes, Det finnes ingen buss i dag is also correct. Finnes (“exists”) sounds a bit more formal or emphatic. Det er ingen buss i dag is more everyday speech.

Why is i dag written as two words and not one like “today” in English?

Historically Norwegian uses the preposition i (“in”) plus dag (“day”) to form i dag (“in day” = today). Modern orthography keeps them separate, unlike English’s single word “today.”

Would you ever say Ingen buss går i dag?

You could say Det går ingen buss i dag, focusing on the action of buses running. Går here means “runs” or “operates.” But the most common, neutral way to state “there is no bus service today” is Det er ingen buss i dag.