3 files changed, 21 insertions, 13 deletions
diff --git a/guides/source/4_1_release_notes.md b/guides/source/4_1_release_notes.md
index a01031ca96..6abbb799c8 100644
--- a/guides/source/4_1_release_notes.md
+++ b/guides/source/4_1_release_notes.md
@@ -457,10 +457,10 @@ for detailed changes.
 
 ### Notable changes
 
-* Default scopes are no longer overriden by chained conditions.
+* Default scopes are no longer overridden by chained conditions.
 
   Before this change when you defined a `default_scope` in a model
-  it was overriden by chained conditions in the same field. Now it
+  it was overridden by chained conditions in the same field. Now it
   is merged like any other scope. [More Details](upgrading_ruby_on_rails.html#changes-on-default-scopes).
 
 * Added `ActiveRecord::Base.to_param` for convenient "pretty" URLs derived from
@@ -547,13 +547,12 @@ for detailed changes.
   ([Pull Request](https://github.com/rails/rails/pull/13350))
 
 * Make `change_column_null`
-  revertable. ([Commit](https://github.com/rails/rails/commit/724509a9d5322ff502aefa90dd282ba33a281a96))
+  revertible. ([Commit](https://github.com/rails/rails/commit/724509a9d5322ff502aefa90dd282ba33a281a96))
 
 * Added a flag to disable schema dump after migration. This is set to `false`
   by default in the production environment for new applications.
   ([Pull Request](https://github.com/rails/rails/pull/13948))
 
-
 Active Model
 ------------
 
diff --git a/guides/source/active_support_core_extensions.md b/guides/source/active_support_core_extensions.md
index 2ad09f599b..5698dc0413 100644
--- a/guides/source/active_support_core_extensions.md
+++ b/guides/source/active_support_core_extensions.md
@@ -157,9 +157,9 @@ Active Support provides `duplicable?` to programmatically query an object about
 
 ```ruby
 "foo".duplicable? # => true
-"".duplicable?     # => true
+"".duplicable?    # => true
 0.0.duplicable?   # => false
-false.duplicable?  # => false
+false.duplicable? # => false
 ```
 
 By definition all objects are `duplicable?` except `nil`, `false`, `true`, symbols, numbers, class, and module objects.
@@ -2719,11 +2719,14 @@ The method `transform_keys` accepts a block and returns a hash that has applied
 # => {"" => nil, "A" => :a, "1" => 1}
 ```
 
-The result in case of collision is undefined:
+In case of key collision, one of the values will be chosen. The chosen value may not always be the same given the same hash:
 
 ```ruby
 {"a" => 1, a: 2}.transform_keys { |key| key.to_s.upcase }
-# => {"A" => 2}, in my test, can't rely on this result though
+# The result could either be
+# => {"A"=>2}
+# or
+# => {"A"=>1}
 ```
 
 This method may be useful for example to build specialized conversions. For instance `stringify_keys` and `symbolize_keys` use `transform_keys` to perform their key conversions:
@@ -2758,11 +2761,14 @@ The method `stringify_keys` returns a hash that has a stringified version of the
 # => {"" => nil, "a" => :a, "1" => 1}
 ```
 
-The result in case of collision is undefined:
+In case of key collision, one of the values will be chosen. The chosen value may not always be the same given the same hash:
 
 ```ruby
 {"a" => 1, a: 2}.stringify_keys
-# => {"a" => 2}, in my test, can't rely on this result though
+# The result could either be
+# => {"a"=>2}
+# or
+# => {"a"=>1}
 ```
 
 This method may be useful for example to easily accept both symbols and strings as options. For instance `ActionView::Helpers::FormHelper` defines:
@@ -2799,11 +2805,14 @@ The method `symbolize_keys` returns a hash that has a symbolized version of the
 
 WARNING. Note in the previous example only one key was symbolized.
 
-The result in case of collision is undefined:
+In case of key collision, one of the values will be chosen. The chosen value may not always be the same given the same hash:
 
 ```ruby
 {"a" => 1, a: 2}.symbolize_keys
-# => {:a=>2}, in my test, can't rely on this result though
+# The result could either be
+# => {:a=>2}
+# or
+# => {:a=>1}
 ```
 
 This method may be useful for example to easily accept both symbols and strings as options. For instance `ActionController::UrlRewriter` defines
diff --git a/guides/source/configuring.md b/guides/source/configuring.md
index eb04007016..2cece90294 100644
--- a/guides/source/configuring.md
+++ b/guides/source/configuring.md
@@ -939,4 +939,4 @@ ActiveRecord::ConnectionTimeoutError - could not obtain a database connection wi
 If you get the above error, you might want to increase the size of connection
 pool by incrementing the `pool` option in `database.yml`
 
-NOTE. As Rails is multi-threaded by default, there could be a chance that several threads may be accessing multiple connections simultaneously. So depending on your current request load, you could very well have multiple threads contending for a limited amount of connections.
+NOTE. If you are running in a multi-threaded environment, there could be a chance that several threads may be accessing multiple connections simultaneously. So depending on your current request load, you could very well have multiple threads contending for a limited amount of connections.