I have a site that ranks well in one of the popular search word in my language. Now I would like to add another popular term, the same topic, but a completely different word. Is it better to do with it's own page under the same domain for, or use the same page? Could it be harmful to the current keyword, if the same page link to a lot of new search term?
Do you mean you want to target several keywords for the same page? If that is the case it will probabaly actually help your rankings on the other keyword. In my experience having anchor text diversity helps alot.