ACF	autocorrelation function	Sa	arithmetic mean height Sa, µm
ACF-CSM	Autocorrelation Function Centre-Shape Method	Sal	auto-correlation length, mm
CPSF	Close Profile Spline Filter	Sbi	surface bearing index
CSSF	Cubic Smoothing Spline Filter	Sci	core fluid retention index
EDM	Empirical Mode Decomposition	Sdq	Root-mean-square gradient
FOD	free of dimple (valley) surface or profile Gauss	Sdr	developed interfacial areal ratio, %
FFTF	Fast Fourier Transform Filter	Sk	core roughness depth, µm
HFN	high-frequency noise	Sku	kurtosis
MA	multithreaded approach	Sp	maximum peak height, µm
MQCL	Minimum Quantity Cooling Lubrication	Spc	arithmetic mean peak curvature, 1/mm
NURBS	non-uniform rational B-spline surfaces	Spd	peak density, 1/mm2
OPGF	Open Profile Gaussian Filter	Spk	reduced summit height, µm
OPSF	Open Profile Spline Filter	Sq	Root-mean-square height, µm
PSD	power spectral density	Ssk	skewness
PSM	Profile Spline Method	Std	texture direction, °
PSWF	Polynomial Spline Wavelet Filter	Str	texture parameter
RSM	root-mean-square	Sv	maximum valley depth, µm
TTP	treatment-trace-profiles approach	Svi	valley fluid retention index
WLIAFM	white light interference-based atomic force microscopy	Svk	reduced valley depth, µm
ω	vector of output data values	Sz	the maximum height of surface, µm
${\lambda }_c$	cut-off value	Ra	arithmetic mean deviation of rough. profile, µm
s(x)	the weighting function	Rc	mean height of roughness profile element, µm
$f$	a “noisy-data” vector	Rdc	roughness profile Section height difference, µm
$f_i$	the example of “noisy data”	Rdq	root-mean-square slope of roughness profile, °
$g\left(x\right)$	cubic spline smoothing curve	Rmr	relative material ratio of roughness profile, %
$g$	a smoothed vector	Rp	maximum peak height of roughness profile, µm
$A$	a symmetric three-diagonal matrix with the non-null elements of the $i$th row or column	RPc	peak count of the raw profile, 1/mm
$c\left(k\right)$	the B-spline coefficients	Rq	root-mean-square (RSM) dev. of r. profile, µm
$B^0\left(x\right)$	the indicator function	RSm	mean width of roughness profile element, mm
$B^n\left(t\right)$	the B-spline function constructed by a repeated convolution of a B-spline of order 0	Rt	total height of roughness profile, µm
${\beta }^n\left(t\right)$	the central B-spline	Rv	maximum valley depth of roughness profile, µm
${\psi }_m\left(t\right)$	the B-spline waelet	Rz	maximum height of roughness profile, µm
$N_m$	$\mathrm{the} m$th order B-spline
$s\left(x,y\right)$	the bi-cubic spline element
$c$	the coefficients $c_{ij}$
$z$	the values of $z_r$
$A$	the Kronecker product of two-band matrices of small size