what's a serious
se·ri·ous [seer-ee-uhs]
adjective
1.
of, showing, or characterized by deep thought.
2.
of grave or somber disposition, character, or manner: a serious occasion; a serious man.
3.
being in earnest; sincere; not trifling: His interest was serious.
4.
requiring thought, concentration, or application: serious reading; a serious task.
5.
weighty or important: a serious book; marriage is a serious matter.