円えん周しゅう率りつえんしゅうりつMeanings1nounpi (π); ratio of circumference to diametermathematicsMathematical constant approximately equal to 3.14159. Used in geometry and formulas.円えん周しゅう率りつは約やく3.14です。Pi is approximately 3.14.円えん周しゅう率りつを使つかって円