Merge pull request #322 from mandeep/data-race-correction

Corrected run-on sentence in data race definition

src/ch04-02-references-and-borrowing.md

@@ -155,13 +155,17 @@ error[E0499]: cannot borrow `s` as mutable more than once at a time
 This restriction allows for mutation but in a very controlled fashion. It is
 something that new Rustaceans struggle with, because most languages let you
 mutate whenever you’d like. The benefit of having this restriction is that Rust
-can prevent data races at compile time. A *data race* is a particular type of
-race condition where two or more pointers access the same data at the same
-time, at least one of the pointers is being used to write to the data, and
-there’s no mechanism being used to synchronize access to the data. Data races
-cause undefined behavior and can be difficult to diagnose and fix when trying
-to track them down at runtime; Rust prevents this problem from happening since
-it won’t even compile code with data races!
+can prevent data races at compile time.
+
+A *data race* is a particular type of race condition where these three things occur:
+
+-  two or more pointers access the same data at the same time
+-  at least one of the pointers is being used to write to the data
+-  there’s no mechanism being used to synchronize access to the data
+
+Data races cause undefined behavior and can be difficult to diagnose and fix
+when trying to track them down at runtime; Rust prevents this problem from
+happening since it won’t even compile code with data races!
 
 As always, we can use `{}`s to create a new scope, allowing for multiple mutable
 references, just not *simultaneous* ones: