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!"
an organization that is a member of another organization (especially a state that belongs to a group of nations); "the library was a member of the interlibrary loan association"; "Canada is a member of the United Nations"
one of the persons who compose a social group (especially individuals who have joined and participates in a group organization); "only members will be admitted"; "a member of the faculty"; "she was introduced to all the members of his family"
anything that belongs to a set or class; "snakes are members of the class Reptilia"; "members of the opposite sex"