text: In geometry , the parallel postulate , also called Euclid 's fifth postulate because it is the fifth postulate in Euclid 's Elements , is a distinctive axiom in Euclidean geometry .
simplified: In geometry the Parallel postulate is one of the axioms of Euclidean geometry . Sometimes it is also called Euclid 's fifth postulate , because it is the fifth postulate in Euclid 's Elements .