informal vs solemn

informal

adj
  • Not formal or ceremonious. 

  • Reflecting everyday, non-ceremonious usage. 

  • Suited for everyday use. 

  • Not in accord with the usual regulations. 

  • Not organized; not structured or planned. 

solemn

adj
  • Characterized by or performed with appropriate or great ceremony or formality. 

  • Of or pertaining to religious ceremonies and rites; (generally) religious in nature; sacred. 

  • Inspiring serious feelings or thoughts; sombrely impressive. 

  • Deeply serious and sombre; grave. 

How often have the words informal and solemn occurred in a corpus of books? (source: Google Ngram Viewer )