Comma (,), not a semi-colon (;).

Author: shaunplee

books/RayTracingInOneWeekend.html

@@ -2810,7 +2810,7 @@
 
 You now have a cool ray tracer! What next?
 
-  1. Lights. You can do this explicitly, by sending shadow rays to lights; or it can be done
+  1. Lights. You can do this explicitly, by sending shadow rays to lights, or it can be done
      implicitly by making some objects emit light, biasing scattered rays toward them, and then
      downweighting those rays to cancel out the bias. Both work. I am in the minority in favoring
      the latter approach.