a	model parameter;
b	model parameter;
cij	polynomial coefficients;
e	number value, e;
i	exponent of the time, indices;
j	exponent of the rotational velocity, indices;
mw	mass lost due to wear;
n	number of experimental data (results);
q	interpolated parameters;
t	time, independent variable;
tμ	conventional lifetime;
w	indices;
xw	string values of the independent variables t and ω;
yw	experimental data values of the material mass lost due to wear;
$\overline{y}$	average values for the experimental data (results) string.
Greek letters
ε	error;
θ	independent variable, angular space, angle;
μ	fractional from the mass lost due to wear;
φ	function;
ω	angle velocity, rotational velocity, independent variable.