Review feedback plus clarification of error definition and should/must

Author: leebyron

spec/Section 7 -- Response.md

@@ -50,45 +50,46 @@ If an error was raised during the execution that prevented a valid response, the
 
 ### Errors
 
-The `errors` entry in the response is a non-empty list of errors, where each
-error is a map.
+The `errors` entry in the response is a non-empty list of errors raised during
+the _request_, where each error is a map of data described by the error result
+format below.
 
-If no errors were raised during the request, the `errors` entry should not be
+If present, the `errors` entry in the response must contain at least one error.
+If no errors were raised during the request, the `errors` entry must not be
 present in the result.
 
-If the `data` entry in the response is not present, the `errors` entry in the
-response must not be empty. It must contain at least one error. The errors it
-contains should indicate why no data was able to be returned.
+If the `data` entry in the response is not present, the `errors` entry must be
+present. It should contain at least one _request error_ indicating why no data
+was able to be returned.
 
 If the `data` entry in the response is present (including if it is the value
-{null}), the `errors` entry in the response may contain a list of all _field
-error_ that were raised during execution. If any _field error_ was raised during
-execution, it should contain the `errors` entry.
+{null}), the `errors` entry must also be present if a _field error_ was raised
+during execution.
 
 **Request errors**
 
-:: A _request error_ is an error raised during a _request_ but before execution
-begins. This may occur due to a parse grammar or validation error in the
-_Document_, an inability to determine which operation to execute, or invalid
-input values for variables.
+:: A _request error_ is an error raised during a _request_ which results in no
+response data. Typically raised before execution begins, a request error may
+occur due to a parse grammar or validation error in the _Document_, an inability
+to determine which operation to execute, or invalid input values for variables.
 
 A request error is typically the fault of the requesting client.
 
-If a request error is raised, execution does not begin and the `data` entry in
-the response must not be present. The `errors` entry must include the error.
+If a request error is raised, the `data` entry in the response must not be
+present. The `errors` entry must include the error.
 
 **Field errors**
 
-:: A _field error_ is raised during the execution of a particular field. This
-may occur due to an internal error during value resolution or failure to coerce
-the resulting value.
+:: A _field error_ is an error raised during the execution of a particular field
+which results in partial response data. This may occur due to an internal error
+during value resolution or failure to coerce the resulting value.
 
 A field error is typically the fault of a GraphQL service.
 
 If a field error is raised, execution attempts to continue and a partial result
 is produced (see [Handling Field Errors](#sec-Handling-Field-Errors)). The
-`data` entry in the response must be present. The `errors` entry should be a
-list of all raised field errors.
+`data` entry in the response must be present. The `errors` entry should include
+this error.
 
 **Error result format**