diff --git a/education/physics/PHYS2220/Electric Charge.md b/education/physics/PHYS2220/Electric Charge.md
index 27464fe..15a4541 100644
--- a/education/physics/PHYS2220/Electric Charge.md	
+++ b/education/physics/PHYS2220/Electric Charge.md	
@@ -31,5 +31,6 @@ An electric dipole consists of two point charges of equal magnitude but opposite
 
 # Continuous Charge Distributions
 It's largely impossible to sum the electric field from every particle in a piece of matter, so the approximation is made that the charge is spread continuously over the distribution.
-- If the charge distribution extends throughout a 3d volume, we describe it in terms of the **volume charge density** $\rho$, with units of $\frac{C}{m^3}$. 
-- For charge distributions spread over surf
\ No newline at end of file
+- If the charge distribution extends throughout a *3d volume*, we describe it in terms of the **volume charge density** $\rho$, with units of $\frac{C}{m^3}$. 
+- For charge distributions spread over *surfaces*, we use **surface charge density** $\sigma$ ($\frac{C}{m^2}$).
+- For charge distributions spread over *lines*, we use **line charge density** $\lambda$ ($\frac{C}{m}$). 
\ No newline at end of file