Questions & Answers about Vi har inte sett honom på en evighet.
Why do we use på instead of i for the duration here?
In Swedish, when you say how long you have not done something, you use the preposition på. If the sentence described a positive ongoing action, like doing something for an eternity, you would use i. Because this sentence is negated by inte, the duration requires på.
Why does inte go between har and sett?
In a standard main clause, the rule is that the negative word inte goes immediately after the first verb. Here, the first verb is the helping verb har, so inte must step right in between it and the main verb sett.
What form of the verb is sett?
sett is the supine form of the irregular verb att se (to see). You always use the supine form together with har (have) or hade (had) to talk about events in the past, exactly like saying 'have seen' in English.
Why is the word honom used instead of han?
honom is the object form of han (he). Because he is the one receiving the action of being seen, he is the object of the sentence. This perfectly matches how we use 'him' instead of 'he' in English.