Roman letters
A α	fourth order tensor that accounts for the stress-rate of strain relationship
a	coefficient for the interpolation of the growth curve
aα	adhesion of the phase α
b	exponent in the pressure-saturations relationship
C ij	non linear coefficient of the discretized capacity matrix
${\mathbf{d}}^{\overline{\overline{\alpha }}}$	rate of strain tensor
$D_{\mathit{\text{eff}}}^{\overline{\mathit{\text{il}}}}$	diffusion coefficient for the species i dissolved in the phase l
$D_{\mathit{\text{eff}}}^{\overline{\mathit{\text{il}}}}$	effective diffusion coefficient for the species i dissolved in the phase l
D s	tangent matrix of the solid skeleton
e s	total strain tensor
${\mathbf{e}}_{\mathit{\text{el}}}^s$	elastic strain tensor
${\mathbf{e}}_{\mathit{\text{vp}}}^s$	visco-plastic strain tensor
${\mathbf{e}}_{\mathit{\text{sw}}}^s$	swelling strain tensor
f v	discretized source term associated to the primary variable v
H	Heaviside step function
K ij	non linear coefficient of the discretized conduction matrix
k αs	absolute permeability tensor of the phase α
$k_{\mathit{\text{rel}}}^{\alpha }$	relative permeability of the phase α
N v	vector of shape functions related to the primary variable v
pα	pressure in the phase α
$p_{\mathit{\text{crit}}}^t$	tumor pressure above which growth is inhibited
$p_{\mathit{\text{necr}}}^t$	tumor pressure above which stress causes an increase of the death rate
r ∞	coefficient for the interpolation of the growth curve: tumor radius at sufficiently large time
rsph	radius of the spheroid
rnc	radius of the necrotic core
R α	resistance tensor
Sα	saturation degree of the phase α
${\mathbf{t}}_{\mathit{\text{eff}}}^{\overline{\overline{s}}}$	effective stress tensor of the solid phase s
${\mathbf{t}}_{\mathit{\text{tot}}}^{\overline{\overline{s}}}$	total stress tensor of the solid phase s
u s	displacement vector of the solid phase s
x	solution vector