fixed typo, wording

Author: bchase

crash-course.markdown

@@ -497,7 +497,7 @@ end
 
 When defining a function with the same name multiple times, each such definition is called a **clause**. In Erlang, clauses always go side by side and are separated by a semi-colon ``;``. The last clause is terminated by a dot ``.``.
 
-Elixir doesn't require punctuation to separate clause, although the must be grouped together.
+Elixir doesn't require punctuation to separate clauses, but they must be grouped together.
 
 ### Function Overloading