Small unstressed words placed just after the finite verb colour the whole sentence: 'jo' signals we both know this, 'vel' softens into a guess, 'nok' means probably, 'da' adds mild insistence. They carry no dictionary meaning of their own - they set the tone and make speech sound native.
Examples
- Det er jo helt umulig å svare på.
- That's impossible to answer, as you know.
- Du kommer vel på festen?
- You're coming to the party, aren't you?
- Det blir nok dyrt å pusse opp.
- Renovating will probably be expensive.
- Kom da, vi er sent ute!
- Come on, we're late!
The mistake to avoid
Stressing them or translating them literally - they are unstressed and their force is tonal, not lexical.
Where this fits in
Uttrykk og nyanser, Norwegian C1: Master register, idiomatic expression, and emotional nuance.