the state of being seriousHe spoke with a seriousness that was unusual in him.We saw from the seriousness of her expression that she meant it.Oxford Collocations Dictionaryadjectivecomplete,deadly,deep,…verb + seriousnessappreciate,grasp,realize,…prepositionwith seriousness phrasesin all seriousness,take, treat, etc. something with the utmost seriousnessSeefull entry
Extra examplesHe maintained an attitude of high seriousness.Only later did he realize the full seriousness of his actions.She spoke with great seriousness of the hardships she had endured.The joke did not obscure the underlying seriousness of his point.The problem was not treated with the seriousness it deserved.The sentence imposed in this case demonstrates the seriousness of environmental crimes.You can’t in all seriousness think they’ll give you the job!He had not understood the seriousness of the matter.Idioms