Premise: Serena Jameka Williams ( born September 26 , 1981 ) is an American professional tennis player . In total , she has been world no. 1 for 319 weeks , which ranks her third in the Open Era among female tennis players . Williams ' accomplishments and success in professional tennis have led some commentators , players , and sports writers to regard her as the greatest female tennis player of all time . Her total of 23 Grand Slam singles titles marks the record for the most Grand Slam wins by a tennis player in the Open Era , and is second on the all-time list behind Margaret Court ( 24 ) .
Hypothesis: Serena Williams is a tennis player.
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