Changing Keywords

Can i change keywords in a free wordpress blog after i publish it?
If not then if i install wordpress in my own site can i change there the keywords?
I mean after a time you might wanna change the keywords for a subdomain's article of your wordpress site and i never looked at that option.
So can i change keyword tags?

can i change keywords?

you can change it if your hosting your own site. But if its on wordpress.com then you cant.

is it meta keywords?
you can edit the template or through seo plugin

and you might want to read this.
http://googlewebmastercentral.blogspot.com/2009/09/google-does-not-use-keywords-meta-tag.html