$\left(x_c^i,y_c^i\right)$	Coordinates of tool edge center in the direction of ${\phi }_i$
$x_j$	The coordinate of the $j$-th point in feed direction
${\phi }_i$	The $i$-th tool rotation angle
${\gamma }_i$	Instantaneous negative rake angle
$h_i$	The instantaneous uncut chip thickness in the direction of ${\phi }_i$
$h_{\min }$	Minimum chip thickness
$h_{\max }$	Maximum uncut chip thickness
Rai	The surface roughness of the i-th discrete region
$\mathsf{\mu }$	Average value of N discrete surface roughness
$r_e$	Tool edge radius
D	The diameter of the milling tool
N	The number of the discrete regions
$A_t^i$	The total volume of tool contact material in the direction of ${\phi }_i$
$A_s^i$, $A_p^i$	The volume of sheared and ploughed material in the direction of ${\phi }_i$
${\mathrm{NSPA}}_i$	The $i$-th normal specific ploughing amount
$\mathsf{\sigma }$	Standard deviation of N discrete surface roughness
$n_f$	The ordinal number of tool flutes
$f_t$	Feed per tooth
d	Depth of cut
$z_e^{ij}$	The height of tool edge profile
N	The number of sampling points of surface roughness
n	Spindle rotation speed
$\alpha$	Tool clearance angle