Old variant of dann. The functional split between denn and dann was prescribed only by the grammarians of the 18th century. In colloquial German, the two words may still overlap. One may hear denn instead of dann in northern Germany, and vice versa in western and southern Germany.
The normal conjunction after a comparative is als; denn is generally archaic. Only in two cases is it still found in contemporary German:
- after als meaning “as, like”, in order to avoid reduplication: Er war nie glücklicher denn als kleiner Junge. — “He was never happier than as a little boy.” This usage is formal.
- after je (“ever before”): Er ist glücklicher denn je. — “He is happier than ever before.” This usage is normal or only slightly formal. The combination als je is not common, but one can say als je zuvor.
- (in a question) then; ever; but; used for general emphasis
- Wo ist er denn? - "Where is he, then?" ("Where ever can he be?")
- Wieso denn? - "How so, then?"
- Was denn? - "But what?"
- Was ist denn los? - "What's wrong, then?"