law: Indian Evidence Act, 1872 
  49. Opinion as to usage, tenets, etc., when relevant 
  When the Court has to
  
  form an opinion as to-
  the usages and tenets
  
  of any body of men or family, the constitution and government of any religious or
  
  charitable foundation, or
  the meaning of words
  
  or terms used in particular districts or by particular or by particular classes
  
  of people, the opinions of persons having special means of knowledge thereon,
  
  we relevant facts.