seriousness  
noun [ U ] uk/ˈsɪə.ri.əs.nəs/ us/ˈsɪr.i.əs.nəs/
  (BAD)      
  严重;恶劣
the state of being very bad or severe
  I don't think he has any idea of the seriousness of the situation. 我认为他一点儿也不明白形势的严峻性。 
 Synonyms: gravity (SERIOUS)severity (SERIOUS)
   (NOT JOKING)      
 严肃;认真
the state of being serious, rather than intending to be funny
  In all seriousness now (= I am now being serious and no longer joking), I do think there's a problem here that we need to straighten out. 现在说正经的——我确实认为这儿有个问题我们得解决。