Suppose I put these seven words in seven squares now. Put them in the first box first. There are seven ways to put them in the first box. Because it can't be repeated, there are only six choices in the second box, and so on. There are five words in the third box.

So the answer is 7×6×5×4×3×2× 1=5040. If you don't know how to start, you can try to change seven words into three words, list the order and find the law.

There should be a formula to solve this problem in the series of high school mathematics textbooks.