Subnotebook vs. UMPC vs. Netbook: WTF Is the Difference?

When Blam broke the news on Dell’s mini Inspiron, there was one thing he was stuck on: How to categorise it. Is it a subnotebook? A UMPC? A netbook? (Knowing the specs might have helped, but probably not much.) Part of the problem is that the category names themselves are very new and pretty vague. Here’s a mini-compendium of the most popular terms for dwarfish laptops being tossed around, where they come from and what they’re trying to say. Help us decide which ones to keep, and which to ditch.