illuminant vs luminous

illuminant

adj

  • That illuminates. 

noun

  • Something that illuminates. 

luminous

adj

  • Brightly illuminated. 

  • Clear; enlightening; easy to understand. 

  • Emitting light; glowing brightly; shining. 

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