Easiest way to remember Universal Design is "UD = EZ for the most people". Commercially, Universal Design, abbreviated UD, has been around for decades (e.g. Velcro, electric toothbrush, automatic doors to retail stores) but North Carolina State's College of Design first introduced UD for the home in 1997.
I begin this series of posts about Universal Design for the home (also referred to as "barrier-free living") by defining as features, methods and applications easily used by any person of any age or ability. Think kid-friendly or flexible enough to be accomplished or enjoyed either seated or standing. For example, most people can get through a wide doorway or hallway, or enter a shower or doorway without a raised threshold. Most people can use motion-activated lights or a lever door handle.
If you remember ONLY ONE thing, recall UD = EZ for every aspect of a property both inside and outside.