It's serious in Latin, French and English! (5)
I believe the answer is:
grave
(Other definitions for grave that I've seen before include "French accent; very serious" , "In which to lay a corpse" , "Grim-faced" , "Sober" , "Sleek, black" .)
I believe the answer is:
grave
(Other definitions for grave that I've seen before include "French accent; very serious" , "In which to lay a corpse" , "Grim-faced" , "Sober" , "Sleek, black" .)