seriousness in WordNet English dictionary

1. the quality of arousing fear or distress
   "he learned the seriousness of his illness"
   seriousness  distressfulness 
   
2. the trait of being serious
   "a lack of solemnity is not necessarily a lack of seriousness"- Robert Rice
   seriousness  earnestness  serious-mindedness  sincerity 
   
3. an earnest and sincere feeling
   earnestness  seriousness  sincerity 
   

seriousness in English Wiktionary