If the child learnt those 2000 by himself, then is really a smart kid, but mostly they don't know the meaning at all. I remember my son used to say word house as home, small as little at 2 year-old plus, so he was learning by the meaning. He did that on his own as well. There is an app named endless words (free part). But when I purchased the app for him, he already no interest and never used it any more. His letter writing was better at 3 year-old than at 5, as he doesn't practice it any more. He used to do many digits additions and subtraction, but much worse now, as he totally stopped that for over 8 months. He also stopped reading during summer. There was a library program to make kids read 15 minutes for 50 days, which interested him in the beginning, but soon he turned against reading and totally stopped it. I now don't get him in those any more. When he had interest, he read 1.5 hours all by himself, sometimes chapter books, but he suddenly stopped everything since the library reading program.