því

From Old Norse því, possibly from the instrumental interrogative Proto-Germanic *hwī (“how, with what”), with the initial h- replaced by the þ- from the forms of *sa.

því

1. because, for, since
   • Colossians 3:9

     Ljúgið ekki hver að öðrum, því þér hafið afklæðst hinum gamla manni með gjörðum hans.

     Do not lie to each other, since you have taken off your old self with its practices.

• af því að, því að (“because”)
• því aðeins að (“only if, on the condition that”)

því

1. (personal) dative singular of það

því...því

1. the...the (when comparing)

   en því meira sem hann blés, því þéttara vafði ferðamaðurinn kápunni að sér

   but the more he blew, the tighter the traveller wrapped his coat around himself

• því miður

Possibly from the instrumental interrogative Proto-Germanic *hwī (“how, with what”), with the initial h- replaced by the þ- from the forms of *sa (“that”). Compare Old English þȳ (“by that; therefore; because; since”, instrumental case of þæt). More at the.

því

1. dative singular of þat

því (not comparable)

1. therefore, for that reason