Delta vs d

Symbol	Definition
$δ m$	Small amount [ $k g$ ]
$Δ m$	Big change [ $k g$ ] ( $m_{2} - m_{1}$ )
$d m$	Small change [ $k g$ ]
$\frac{d m}{d t}$	Time derivative [ $\frac{k g}{s}$ ]
$\dot{m}$	Rate [ $\frac{k g}{s}$ ]
$m^{″}$	Flux = per unit area per time [ $\frac{k g}{m^{2} s}$ ]