serious
- 1Important and weighty; significant enough to demand attention or concern.
The company is facing serious financial trouble this quarter.
Doctors found a serious problem with his heart valve.
Similarsevere, grave, major, significant, critical
Oppositeminor, trivial, slight, insignificant
- 2Genuinely meaning what one says or plans; in earnest, rather than joking or deceiving.
She was serious about moving abroad next year.
He made a serious offer to buy the house at full price.
UsageOften serious about something or about doing something: serious about moving abroad.
Similarsincere, earnest, genuine
Oppositeinsincere
Note
Here the question is intention, not expression. "Is he serious?" asks whether someone means it, not whether they are smiling. A person can joke with a straight face, so this sense and the grave, humorless one come apart easily. It also extends to things given in earnest. Serious attention and a serious offer are real ones, not token gestures.
Checked 5 Nov 2026 · 1 fact
- People can deliver jokes without smiling or showing emotion. en.wikipedia.org
- 3Notably big, substantial, or impressive, whether the measure is amount, degree, or quality.
They put serious money into the renovation, and it shows.
This is serious coffee, nothing like the watery stuff from the office machine.
UsageUsually before a noun: serious money, some serious skills, a serious amount of snow.
Similarreal, substantial, considerable
Oppositepaltry
- 4Sincerely committed, especially to a relationship or to a chosen pursuit.
Are the two of them serious, or just casually dating?
He's a serious athlete who trains six days a week.
UsageOften serious about someone or something; when two people get serious, their relationship becomes committed.
Similarcommitted, dedicated, devoted, determined
Oppositecasual, uncommitted, halfhearted
- 5Grave in manner or disposition, showing no humor or sign of cheerfulness.
His serious tone made the whole room fall silent.
The judge stayed serious as she read out the verdict.
UsageAfter look, stay or seem, use serious (not
incorrect: look seriously); it is often strengthened as deadly serious.Similarsolemn
Oppositelighthearted, cheerful, playful, jovial
Note
The sense closest to the word's roots: Latin sērius meant "grave, earnest," and it is usually traced to an Indo-European root meaning "heavy," the same root behind German schwer. A serious face looks as if it is carrying weight. Earnest and solemn sit close by, but serious names a manner, and a manner can break, as when a stern captain suddenly laughs.
Less common meaning
- 6Earnestly or in a grave manner; used colloquially in place of "seriously," most often in "take serious" or "mean serious."
Folks down here don't take outsiders serious at first.
She told him she meant it serious this time.
UsageMost often in take something serious or mean it serious; in careful writing, use seriously.
Note
Ray Lawler gives it to Emma, Olive's mother, in Summer of the Seventeenth Doll (1957): "youse don't take it serious." The form without -ly suits the play's working-class Melbourne voices. In careful writing, seriously is the usual choice.
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Origin
Latin sērius ('grave, earnest, serious') was extended in Medieval Latin to sēriōsus, which, with Old French serieux, lies behind Middle English seryows. Most accounts trace sērius to a Proto-Indo-European root meaning 'heavy', making it a relative of German schwer ('heavy, difficult') and Old English swǣr ('heavy, grave'), though that connection is disputed.