pi
"A dimensionless unit which denoted an irrational real number, approximately equal to 3.14159 which is the ratio of a circle's circumference to its diameter in Euclidean geometry." [Wikipedia:Wikipedia]
pi based unit
pi
"A dimensionless unit which denoted an irrational real number, approximately equal to 3.14159 which is the ratio of a circle's circumference to its diameter in Euclidean geometry." [Wikipedia:Wikipedia]