solemn vs thoughtful

solemn

adj
  • Inspiring serious feelings or thoughts; sombrely impressive. 

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

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

  • Deeply serious and sombre; grave. 

thoughtful

adj
  • Demonstrating kindness or consideration for others. 

  • Demonstrating thought or careful consideration. 

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