a  center distance between base circle and rolling circle  h  radius ratio of enveloping circle and rolling circle 
k  reciprocal of curtate ratio  K  curtate ratio 
L  distance from the point C to the center of rolling circle O_{2}  r_{1}  radius of base circle 
r_{2}  radius of rolling circle  R  radius of enveloping circle (or cutter circle) 
Q  instantaneous flow rate  φ_{1}  rotary angle of base circle 
φ_{2}  rotary angle of rolling circle  θ  angle between line O_{2}C and normal PC of trochoid 
σ_{Q}  pulsation coefficient of flow rate 

