diff --git a/lib/plug/debugger.ex b/lib/plug/debugger.ex
index b3d2a55a..3b936d07 100644
--- a/lib/plug/debugger.ex
+++ b/lib/plug/debugger.ex
@@ -64,7 +64,7 @@ defmodule Plug.Debugger do
 
   ## Custom Banners
 
-  You may pass a MFA (`{module, function, args}`) to be invoked when an
+  You may pass an MFA (`{module, function, args}`) to be invoked when an
   error is rendered which provides a custom banner at the top of the
   debugger page. The function receives the following arguments, with the
   passed `args` concatenated at the end:
@@ -496,7 +496,7 @@ defmodule Plug.Debugger do
 
       {:ok, other} ->
         raise ArgumentError,
-              "expected :banner to be a MFA ({module, func, args}), got: #{inspect(other)}"
+              "expected :banner to be an MFA ({module, func, args}), got: #{inspect(other)}"
 
       :error ->
         nil
diff --git a/lib/plug/session/cookie.ex b/lib/plug/session/cookie.ex
index 9dd5566a..7b7dcf13 100644
--- a/lib/plug/session/cookie.ex
+++ b/lib/plug/session/cookie.ex
@@ -26,11 +26,11 @@ defmodule Plug.Session.COOKIE do
 
     * `:encryption_salt` - a salt used with `conn.secret_key_base` to generate
       a key for encrypting/decrypting a cookie, can be either a binary or
-      a MFA returning a binary;
+      an MFA returning a binary;
 
     * `:signing_salt` - a salt used with `conn.secret_key_base` to generate a
       key for signing/verifying a cookie, can be either a binary or
-      a MFA returning a binary;
+      an MFA returning a binary;
 
     * `:key_iterations` - option passed to `Plug.Crypto.KeyGenerator`
       when generating the encryption and signing keys. Defaults to 1000;
diff --git a/lib/plug/static.ex b/lib/plug/static.ex
index 8e97785a..8ffb7d48 100644
--- a/lib/plug/static.ex
+++ b/lib/plug/static.ex
@@ -12,7 +12,7 @@ defmodule Plug.Static do
       atom representing the application name (where assets will
       be served from `priv/static`), a tuple containing the
       application name and the directory to serve assets from (besides
-      `priv/static`), or a MFA tuple.
+      `priv/static`), or an MFA tuple.
 
   The preferred form is to use `:from` with an atom or tuple, since
   it will make your application independent from the starting directory.