tour n 1. (of a band etc.) turné m 2. (sightseeing) rundreise m/f, rundtur m 3. (museum etc.) of sth omvisning m/f på et sted, av noe phr circular tour rundtur m, rundreise m/f city tour byrundtur m give sb a tour of sth vise noen rundt i noe (package) tour pakketur m, chartertur m
trip n 1. (outing etc.) tur m, utflukt m/f 2. (voyage etc.) reise m 3. (act of tripping) snuble m v 1. over sth snuble i noe 2. trip sb (up) spenne bein for noen, få noen til å snuble phr boat trip sjøreise m/f business trip forretningsreise m/f, tjenestereise m/f
It's about the way things are expressed in each language. If an English speaker is finishing work on a Friday, they would typically say to their colleagues "have a good weekend!", rather than just "good weekend!". A Norwegian would just say "god helg!", and be understood in the same way - the 'ha en' is unspoken, but understood.
Same for 'good trip'. In English, we say "have a good trip!" to a friend who is going on holiday/vacation - we don't just say "good trip!" (although we might say 'bon voyage', which is similar to the Norwegian in omitting the 'have a').