An	Nominal contact area
Ar	Real contact area
$\overline{A}$	Single asperity contact area
ω	Interference between surfaces
ωc	Critical interference
Sy	Yield strength
E	Elastic modulus
ν	Poisson’s ratio
E’	Effective elastic modulus, E/(1 − ν2)
$\overline{F}$	Single asperity contact force
η	Asperity density
R	Asperity radius
σs	RMS Asperity Height
f	Spatial frequency
$\lambda$	Wavelength of sinusoidal surface (1/f)
Δ	Amplitude of sinusoidal surface
$\overline{p}$	Average pressure over surface
p*	Average pressure for complete elastic contact
p*ep	Average pressure for complete elastic-plastic contact