$Q_t$	amount of drug released at time t
$Q_0$	initial amount of drug in the solution (usually $Q_0=0$)
$Q_{\infty }$	total amount of drug released (≈total amount in the dosage system)
$C_t$	drug concentration at time t
$C_0$	initial drug concentration
$C_T$	total drug concentration
$C_s$	saturation concentration (solubility) of drug at given temperature
$C_{lip}$	initial amount of drug encapsulated in the DDS
$C_{ms}$	drug solubility in the matrix
$W_0$	initial amount of drug encapsulated in the DDS
$W_t$	amount of drug remaining in the DDS at time t
$X_t$	percentage release at time t
$X_{max}$	maximum dissolution
$A$	surface area of the DDS
D	diffusion coefficient
$K^{\prime }$	constant related to surface, shape, and density of particles
$N$	number of particles
$\delta$	thickness of the diffusion layer
$r_0$	radius of a spherical matrix
$a_0$	half thickness of the system
$1/a$	timescale parameter
$b$	shape parameter (release curve in Weibull, dissolution rate in Gompertz, and nanoparticles shape in Hopfenberg)
$c$	equivalence of undissolved proportion at time t = 1
$k_{er}$	erosion rate constant
$k_i$	model release constants 1
1$k_{i}refersto{k}_0,k_1,k_h,k_{hc},k_{kp},k_{bl},k_g,k_{hf},k_{lh1/2}$