I've always referred to the additions to Settlers of Catan that adds Settlers of Catan support as Extensions. It's what's printed on the 4th edition box. I've noticed though, Catan and Seafarers 5-6 player expansion that it was changed to call it an expansion. I've corrected the text back in the post, but it's got me thinking. What's the correct terminology for these additions? Expansion or extension?
Also, are there any other games that add support for more players like Settlers of Catan, and how do they refer to these additions.