Fix spelling in structure.rst

Author: campbellr

docs/writing/structure.rst

@@ -279,7 +279,7 @@ clearer and thus preferred.
 Using this mechanism is useful for separating concerns and avoiding
 external un-related logic 'polluting' the core logic of the function
 or method. A good example of a piece of functionality that is better handled
-with decoration is memoization or caching: you want to store the results of an
+with decoration is memorization or caching: you want to store the results of an
 expensive function in a table and use them directly instead of recomputing
 them when they have already been computed. This is clearly not part
 of the function logic.