Language code or other custom string for pattern matching within the path. With language negotiation set to <em>Path prefix only</em> or <em>Path prefix with language fallback</em>, this site is presented in this language when the Path prefix value matches an element in the path. For the default language, this value may be left blank. <strong>Modifying this value will break existing URLs and should be used with caution in a production environment.</strong> <em>Example: Specifying "deutsch" as the path prefix for German results in URLs in the form "www.example.com/deutsch/node".</em>