requiring effort or concentration; complex and not easy to answer or solve; "raised serious objections to the proposal"; "the plan has a serious flaw"
of great consequence; "marriage is a serious matter"
concerned with work or important matters rather than play or trivialities; "a serious student of history"; "a serious attempt to learn to ski"; "gave me a serious look"; "a serious young man"; "are you serious or joking?"; "Don't be so serious!"
continuing or enduring without marked change in status or condition or place; "permanent secretary to the president"; "permanent address"; "literature of permanent value"
not capable of being reversed or returned to the original condition; "permanent brain damage"