Redirecting url to access subdirectory

Solution:

To rewrite / to /wordpress you can use this rule :

RewriteEngine On
RewriteCond %{HTTP_HOST} ^(www\.)?domain.com$
RewriteCond %{REQUEST_URI} !^/wordpress
RewriteRule ^(.*)$ /wordpress/$1 [L]

This will internally redirect all requests from root to the subfolder. Do not remove the RewriteCond directive otherwise the the rewrite destination will rewrite back to itself causing an infinite loop error.