This is the 530th most frequent Icelandic word.
farþega
Passenger.
Here, 'farþegarnir' is the plural form (nominitive masculine) of 'farþegi' meaning 'passengers', used as the subject of the sentence.
Farþegarnir biðu rólegir eftir rútunni.
The passengers waited calmly for the bus.
In this sentence, 'farþegum' is the plural dative form of 'farþegi', used as the indirect object receiving the action.
Stjórinn á rútunni sagði farþegum að setjast niður.
The bus driver told the passengers to sit down.
Here, 'farþegaðjónustan' is a compound noun formed from 'farþega', relating it to the 'service' being offered to passengers.