serious

From WikiWord, the free dictionary

/ˈsɪə.ɹi.əs/ English

Definitions

Without humor or expression of happiness; grave in manner or disposition“It was a surprise to see the captain, who had always seemed so serious, laugh so heartily.”
Important; weighty; not insignificant“This is a serious problem. We'll need our best experts.”
Really intending what is said (or planned, etc); in earnest; not jocular or deceiving“After all these years, we're finally getting serious attention.”
(of a relationship) Committed.