How to redirect www.subdomain.domain.com to subdomain.domain.com?

Could anybody please tell me how to set .htaccess rewrite rules to redirect https://www.subdomain.domain.com to subdomain.domain.com ? Thanks.

In my WordPress MU, https://www.subdomain.domain.com is redirected to https://www.domain.com (I use www for the top domain) by default. But I’d like to set .htaccess to redirect https://www.subdomain.domain.com to subdomain.domain.com . Otherwise I can’t set the preferred domain in Google Webmaster Tools because Google Webmaster Tools thinks the two domains, https://www.subdomain.domain.com and subdomain.domain.com, are not of the same content.