Of course, the DL's dog eats the cat many times ...
so "Glad" and "Lycklig" both mean happy
are they interchangeable ?
They represent different feelings.
glad is a more short-term happiness, like merry. You're likely to laugh when you're glad.
lycklig is a bigger feeling, more to do with fulfillment.
In some expressions, only one of them works.
In addition to what Arnauti said, something for speakers/learners of german:
"glad" and "lycklig" are "fröhlich" and "glücklich", I believe.
Notice that english "glad" is "froh" in german. Also, "färgglad"="farbenfroh".
In Dutch: glad=blij and lycklig=gelukkig (?)
Does glad not mean glad?
It’s usually better translated with ’happy’, but it can correspond to English ’glad’ as well.
Just because it didn't accept glad.
Added it now. :)