serious

1. 1
   severeadjective

   Very important and needing careful thought, not small.

   Like a warning light on a car that you must not ignore.

   Climate change is a serious problem for everyone.

   We have a serious decision to make before Friday.

   Similarsevere, grave, major, significant, critical

   Oppositeminor, trivial, slight, insignificant

2. 2
   means businessadjective

   Truly meaning what you say, and not joking around.

   Are you serious about quitting your job?

   I'm serious. I really did see a bear in the yard.

   UsageSay serious about something or about doing something.

   Similarsincere, earnest, genuine

   Oppositeinsincere

   Note
3. 3
   adjectivecolloquial

   Very big or very good in amount, level, or quality.

   We got a serious amount of snow last night.

   That kid has some serious skills on a skateboard.

   UsageUsually comes before a noun, as in serious money or some serious skills.

   Similarreal, substantial, considerable

   Oppositepaltry

4. 4
   adjective

   Truly committed to a person or a goal you care about.

   They've been in a serious relationship for two years.

   She's serious about her training and never misses a day.

   UsageSay serious about someone or something. When two people get serious, they become committed to their relationship.

   Similarcommitted, dedicated, devoted, determined

   Oppositecasual, uncommitted, halfhearted

5. 5
   adjective

   Not cheerful or playful, with no joking or smiling.

   Like a face at a funeral, with no joking or smiling.

   She had a serious look on her face all morning.

   Why are you so serious today?

   UsageSay look serious (not incorrect: look seriously). Deadly serious means very serious.

   Similarsolemn

   Oppositelighthearted, cheerful, playful, jovial

   Note

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