Goddag
Means "Hallo"
A more unformal way to say Hallo is to use the word "Hej". This can also be used in the meaning "Goodbye"

Farvel
Means "Goodbye". You can also use the word "Hej" as goodbye which is more unformal.

Tak
Means "Thank you". "Mange tak" means "Thank you very much"

Undskyld
Means "Sorry"

Skål
Means "Cheers"