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serious - definition and synonyms


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adjective serious pronunciation in American English /ˈsɪriəs/
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  1. 1
    bad or dangerous enough to make you worried
    a serious illness/accident/injury: a serious head injury
    a serious problem/mistake: It’s not a serious problem – we should be able to fix it easily.
    a serious crime/offense/threat: An accident like this poses a serious threat to the environment.
    The sale of the company will have serious implications for people’s jobs.
  2. 2
    important and deserving attention
    This is an extremely serious matter.
    He has no serious competition for the job.
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  3. 3
    meaning what you say or do, and not making a joke
    I’m sorry, I didn’t realize you were being serious.
    The police have made no serious attempt to address these issues.
    serious about: I’m not convinced they’re serious about the deal.
    serious about (doing) something: Do you think Mike’s serious about going to live in New York?
    deadly/dead (=completely) serious: “Are you serious about leaving your job?” “Dead serious.”
  4. 4
    careful and detailed
    serious consideration/thought/discussion: We’ll have to give the situation some serious thought.
  5. 5
    someone who is serious thinks carefully about things and does not laugh much
    Peter seems serious but he actually has a good sense of humor.
    1. a.
      appearing worried or upset
      Is Mary all right? She looked a little serious.
  6. 6
    [usually before noun] dealing with important, complicated, or difficult ideas or subjects
    serious books/music
  7. 7
    if you are in a serious romantic relationship with someone, you intend to stay together for a long time
    Is it getting serious with you and June?
    a serious boyfriend/girlfriend/relationship: He’s never had a serious relationship with anyone.
  8. 9
    informal extreme, or large in amount
    We did some serious hiking last weekend.
    It’s time you made some serious money.


derived word


a course of study which is much shorter than a university course and focuses on the skills you need for a job, especially computer-related skills

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an ancient Roman system of underfloor heating, used to heat houses with hot air; from the Latin 'hypocaustum'

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