illegitimate vs valid

illegitimate

adj
  • Not sanctioned by marriage. 

  • Not correctly deduced. 

  • Not authorized by good usage; not genuine. 

  • Involving the fertilization of pistils by stamens not of their own length, in heterogonously dimorphic and trimorphic flowers. 

  • Not conforming to known principles, or established or accepted rules or standards. 

  • Born to unmarried parents. 

  • Not in accordance with the law. 

noun
  • A person born to unmarried parents. 

verb
  • To make illegitimate. 

valid

adj
  • Well grounded or justifiable, pertinent. 

  • Of an argument: whose conclusion is always true whenever its premises are true. 

  • Genuine - as distinguished from efficient or regular - sacrament. 

  • Related to the current topic, or presented within context, relevant. 

  • Of a formula or system: such that it evaluates to true regardless of the input values. 

  • Acceptable, proper or correct; in accordance with the rules. 

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