update description of volatile

docs/csharp/language-reference/keywords/volatile.md

@@ -9,7 +9,7 @@ helpviewer_keywords:
 ms.assetid: 78089bc7-7b38-4cfd-9e49-87ac036af009
 ---
 # volatile (C# Reference)
-The `volatile` keyword indicates that a field might be modified by multiple threads that are executing at the same time. Fields that are declared `volatile` are not subject to compiler optimizations that assume access by a single thread. This ensures that the most up-to-date value is present in the field at all times.  
+The `volatile` keyword indicates that a field might be modified by multiple threads that are executing at the same time. Fields that are declared `volatile` are not subject to compiler optimizations that assume access by a single thread. These restrictions ensure that all threads will observe volatile writes performed by any other thread in the order in which they were performed. There is no guarantee of a single total ordering of volatile writes as seen from all threads of execution.  
 
  The `volatile` modifier is usually used for a field that is accessed by multiple threads without using the [lock](../../../csharp/language-reference/keywords/lock-statement.md) statement to serialize access.