Your problem is likely not to be the word show
and more likely to be the underscore in show_album
- your patterns in htaccess
won't match underscores.
Try the following patterns with underscores added.
#mod_rewrite start
Options +FollowSymLinks
RewriteEngine on
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^([a-zA-Z_]*)/?([a-zA-Z_]*)?/?([a-zA-Z0-9_]*)?/?$ index.php?controller=$1&action=$2&id=$3 [QSA,L]
#mod_rewrite end