Clean up formatting and some grammar

wiki/Mapping_Techniques/Overlap/en.md

@@ -1,7 +1,7 @@
 # Overlap
 
-![](./img/overlap.jpg "An example of a hitcircle overlapping a sliderhead.")
+![](img/overlap.jpg "An example of a hit circle overlapping a slider head.")
 
-An overlap appears when [hit objects](/wiki/Hit_Objects) touch each other without stacking.<!--TODO: Insert link to stacking article when it exists-->
+An **overlap** appears when [hit objects](/wiki/Hit_Objects) touch each other without [stacking](/wiki/Mapping_Techniques/Stack).
 
 <!-- this is a stub -->

wiki/Mapping_Techniques/Stack/en.md

@@ -1,11 +1,9 @@
----
-stub: true
----
-
 # Stack
 
-![](./img/stack.jpg "An example of two circles stacking ontop of a sliderhead.")
+![](img/stack.jpg "An example of two hit circles stacking on top of a slider head.")
+
+A **stack** is a set of [hit objects](/wiki/Hit_Objects) that [overlap](/wiki/Mapping_Techniques/Overlap) each other in the playfield<!-- TODO: link -->. The most common objects that are stacked are [hit circles](/wiki/Hit_Objects#hit-circle).
 
-A stack refers to [hit objects](/wiki/Hit_Objects) that [overlap](/wiki/Mapping_Techniques/Overlap) each other in the playfield. The most common object that is stacked are hit circles.
+Stacks are automatically created when hit objects are close to perfectly overlapping each other. The time between objects for this to occur is determined by the [beatmap](/wiki/Beatmaps)'s stack leniency<!-- TODO: link -->.
 
-Stacks are automatically created when hit objects are close to perfectly overlaping each other. The time between objects for this to occur is determined by stack leniency.
+<!-- this is a stub -->