Merging terms in any taxonomy can be tricky. There are a number of concerns: why are we merging the two terms to begin with? How do we know which term should be the Preferred Term? What happens to information objects already tagged with the term that is to be demoted? What happens if a user searches on the demoted term?
All of these questions — and more — need to be addressed before merging two terms. One other consideration is whether or not merging terms is a practice documented in your taxonomy governance best practice guide. (Don’t have one? Don’t worry. We’re going to post about taxonomy governance in a few weeks).
If you’re planning to merge terms in your SharePoint 2010 taxonomies, however, it’s not that difficult to do. Check out this video as Isaac shows you how to merge terms, and what the resulting term looks like and how it behaves.