Let me define "most important words". It's not like "commonest words", so it definitely excludes "simple words" like "a, the, so, very...". However, they are still "common vocabulary" that we use everyday. They are powerful. If you fully grasp them, you will improve your expression skills. I think they are words like "challenge...". My question is, do you happen to know some online resource like that? (It don't have to be "1000 most important words".) Thanks.