diff --git a/lib/eex/test/eex_test.exs b/lib/eex/test/eex_test.exs
index beffc520df..a8e5074303 100644
--- a/lib/eex/test/eex_test.exs
+++ b/lib/eex/test/eex_test.exs
@@ -128,7 +128,7 @@ defmodule EExTest do
     end
   end
 
-  test "raises a syntax error when nested end expression is found without an start expression" do
+  test "raises a syntax error when nested end expression is found without a start expression" do
     assert_raise EEx.SyntaxError, "unexpected token: ' end ' at line 1", fn ->
       EEx.compile_string "foo <% if true do %><% end %><% end %>"
     end
diff --git a/lib/elixir/lib/gen_event.ex b/lib/elixir/lib/gen_event.ex
index f5004d0e72..56835192ef 100644
--- a/lib/elixir/lib/gen_event.ex
+++ b/lib/elixir/lib/gen_event.ex
@@ -8,7 +8,7 @@ defmodule GenEvent do
 
   An event manager implemented using this module will have a standard
   set of interface functions and include functionality for tracing and
-  error reporting. It will also fit into an supervision tree.
+  error reporting. It will also fit into a supervision tree.
 
   ## Example
 
diff --git a/lib/elixir/lib/supervisor.ex b/lib/elixir/lib/supervisor.ex
index 4d1f631d9f..1ccdbba0ae 100644
--- a/lib/elixir/lib/supervisor.ex
+++ b/lib/elixir/lib/supervisor.ex
@@ -9,7 +9,7 @@ defmodule Supervisor do
 
   A supervisor implemented using this module will have a standard set
   of interface functions and include functionality for tracing and error
-  reporting. It will also fit into an supervision tree.
+  reporting. It will also fit into a supervision tree.
 
   ## Example