serious

Etymology

From Middle English seryows, from Old French serieux, from Medieval Latin sēriōsus, an extension of Latin sērius (“grave, earnest, serious”), from Proto-Indo-European *swer- (“heavy”). Cognate with German schwer (“heavy, difficult, severe”), Old English swǣr (“heavy, grave, grievous”). More at swear, sweer.

adj

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

adv

1. (colloquial, dialect) In a serious manner; seriously.
   The only time I walk out on singin' is when there's muckin' about and youse don't take it serious. 1957, Ray Lawler, Summer of the Seventeenth Doll, Sydney: Fontana Books, published 1974, page 68