I am a native English speaker, but I ran across this app in Appsniper. I love free apps and I thought this might be cool just to test my own knowledge and see how helpful it could be to someone learning English. There were a couple of words I didn't know the definition of and I was kinda excited about that. The problem is that the program will tell you what % of words you don't know, but that is it. I think that for this to be a decent app, there should be definitions for the words you don't know. Otherwise this is just a list of words. Doesn't seem like it would be very helpful at all. For someone working on their English, they would have to write down all the words they didn't know and then go look them up somewhere else.