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English definition of “serious”

serious

adjective (NOT JOKING)    /ˈsɪə.ri.əs/ US  /ˈsɪr.i-/
B1 not joking or intended to be funny: Please don't laugh - I'm being serious. He was wearing a very serious expression and I knew something was wrong. On the surface it's a very funny novel but it does have a more serious underlying theme.Lacking humour B1 A serious person is quiet, thinks carefully about things, and does not laugh a lot: I remember her as a very serious child.Lacking humour
(Definition of serious adjective (NOT JOKING) from the Cambridge Advanced Learner's Dictionary & Thesaurus © Cambridge University Press)
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