plain vs proven

plain

adj
  • Downright; total, unmistakable (as intensifier). 

  • Clear; unencumbered; equal; fair. 

  • Not a trump. 

  • Containing no extended or nonprinting characters (especially in plain text). 

  • Not unusually beautiful; unattractive. 

  • Evident to one's senses or reason; manifest, clear, unmistakable. 

  • Honest and without deception; candid, open; blunt. 

  • Simple in habits or qualities; unsophisticated, not exceptional, ordinary. 

  • Ordinary; lacking adornment or ornamentation; unembellished. 

  • Having only few ingredients, or no additional ingredients or seasonings; not elaborate, without toppings or extras. 

  • Of just one colour; lacking a pattern. 

adv
  • Simply. 

noun
  • A lamentation. 

  • An expanse of land with relatively low relief, usually exclusive of forests, deserts, and wastelands. 

proven

adj
  • Having been proved; having proved its value or truth. 

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