leading vs number one

leading

adj
  • Ranking first. 

  • Providing guidance or direction. 

  • Occurring in advance; preceding. 

noun
  • Vertical space added between lines; line spacing. 

  • An act by which one is led or guided. 

number one

adj
  • First; foremost; best, often used after its headword. 

noun
  • The main goalkeeper of a team, so-called because they wear the number 1 on the back of their kit. 

  • The most important person, the one who is in charge. 

  • Urine; urination. 

  • A large town where theatrical performances may expect to achieve success. 

  • Used other than figuratively or idiomatically: see number, one. 

  • Oneself, being considered foremost, as by an egoist. 

  • Someone who is top of a ranking, who is ranked first. 

  • The batsman who opens the batting. 

  • The single that has sold the most in a given period. 

  • A first lieutenant. 

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