Fixed even more typos.
@@ -156,7 +156,7 @@ the numerical integrator and the neural network. The solutions are qualitativel
### Poisson's equation
Poisson's equation is a second-order linear PDE. It can be used to describe the potential field caused by a given charge
-or mass density distribution. In a two dimensional Cartesian coordinates, it takes the form:
+or mass density distribution. In two dimensional Cartesian coordinates, it takes the form:
$$
\left(\frac{\partial^2}{\partial x^2} + \frac{\partial^2}{\partial y^2}\right)u(x, y) = f(x, y).
$$
