Hindi: सम्मेलन
Kannada: ಸಮ್ಮೇಳನ where "La" sound is "retroflex"
I think Hindi is closer here to the Tatsama
Don't think the retroflex is there in Sanskrit
సమ్మేళనం
Not sure about Malayalam.
I dont think this word is used all that widely in Tamil
But do we have a lot of words that use it in classical sanskrit? What I hear is - the retroflex La is more common in Vedic language than in Sanskrit.
Not sure how true is that