How to change these words in URL?

[webmastersun]

Hello,

I want to change 2 words "forums" and "threads" in URLs below to other words

for example:

http://www.webmastersun.com/forums/95-Web-Hosting

and

http://www.webmastersun.com/threads/894-Godaddy-Vs-Name-com-which-is-better

I want to change
forums -> category
threads -> topic

I tried to change in .htacess file but it didn't work, I think it need to change in vB codes too.

Can any one support me where and how to edit this?


Thanks in advance!