There are a lot of words and some people don't understand all of them. If you want to write for them, you can use this simple words checker by Randall Munroe (the person who writes XKCD).
Also, watch out for his new book 'A Thing Explainer' that is written with simple words. The book will have pictures with words like this one about a space car. You can find more information about the book here.
Does anyone speak Toki Pona? :-)