Jeg ringer deg i kveld.

Ringer is the present tense of the infinitive å ringe, which means “to call” (on the phone) or “to ring” (like a bell). In Norwegian, the present tense ending –er is used for all persons:

• jeg ringer
• du ringer
• han/hun ringer
• vi ringer
• dere ringer
• de ringer

Here, ringer simply indicates the action (calling) is happening or planned.

In Norwegian (as in English “I’m calling you tonight”), the present tense often expresses a fixed or scheduled action in the near future. Context and time adverbials like i kveld make it clear you mean “this evening.” If you want to be more explicit about the future, you can add the auxiliary skal:

• Jeg ringer deg i kveld. → I’ll call you this evening.
• Jeg skal ringe deg i kveld. → I’m going to call you this evening.

Both sentences convey “I will call you this evening,” but:

• Jeg ringer deg i kveld uses the simple present to state a scheduled action.
• Jeg skal ringe deg i kveld uses skal to emphasize intention or future plan.

In everyday conversation they’re often interchangeable.

The i in i kveld means “in” and forms a time expression equivalent to “this evening” or “tonight.” Norwegian often uses i with time words:

• i dag (today)
• i morgen (tomorrow)
• i natt (tonight)

It tells us when the action takes place.

• i kveld = “this evening” (tonight), a specific reference to the coming evening.
• på kvelden = “in the evening,” more general or habitual (something you do in evenings regularly).

Example:
• I kveld skal jeg spise pizza. (Tonight I’m going to eat pizza.)
• På kvelden ser jeg alltid nyheter. (In the evenings I always watch the news.)

Yes. Norwegian follows the V2 (verb-second) rule: if a time adverbial comes first, the finite verb must come next, followed by the subject:

• I kveld ringer jeg deg.

You cannot say I kveld jeg ringer deg because the verb must stay in second position.

No. Time expressions with i drop the article and use the noun in its base form:

• i kveld = tonight
• i dag = today

By contrast, på kvelden (“in the evening,” general/habitual) uses the definite form kvelden because på requires the noun to be definite or accompanied by an article.