diff --git a/src/Symfony/Component/Console/Input/InputDefinition.php b/src/Symfony/Component/Console/Input/InputDefinition.php
index ffae4fe971..9551e968c4 100644
--- a/src/Symfony/Component/Console/Input/InputDefinition.php
+++ b/src/Symfony/Component/Console/Input/InputDefinition.php
@@ -113,7 +113,7 @@ class InputDefinition
     public function addArgument(InputArgument $argument)
     {
         if (isset($this->arguments[$argument->getName()])) {
-            throw new \LogicException(sprintf('An argument with name "%s" already exist.', $argument->getName()));
+            throw new \LogicException(sprintf('An argument with name "%s" already exists.', $argument->getName()));
         }
 
         if ($this->hasAnArrayArgument) {
@@ -262,9 +262,9 @@ class InputDefinition
     public function addOption(InputOption $option)
     {
         if (isset($this->options[$option->getName()]) && !$option->equals($this->options[$option->getName()])) {
-            throw new \LogicException(sprintf('An option named "%s" already exist.', $option->getName()));
+            throw new \LogicException(sprintf('An option named "%s" already exists.', $option->getName()));
         } elseif (isset($this->shortcuts[$option->getShortcut()]) && !$option->equals($this->options[$this->shortcuts[$option->getShortcut()]])) {
-            throw new \LogicException(sprintf('An option with shortcut "%s" already exist.', $option->getShortcut()));
+            throw new \LogicException(sprintf('An option with shortcut "%s" already exists.', $option->getShortcut()));
         }
 
         $this->options[$option->getName()] = $option;
@@ -280,6 +280,8 @@ class InputDefinition
      *
      * @return InputOption A InputOption object
      *
+     * @throws \InvalidArgumentException When option given doesn't exist
+     *
      * @api
      */
     public function getOption($name)