What are Nick's most important words that he says in the book Frindle?

The most important word in the book Frindle by Andrew Clements is the word frindle itself. In some ways, the circumstances surrounding the creation of the word change the path of Nick's life.
When Nick's teacher, Mrs. Granger, assigns Nick an oral report on where the words in the dictionary come from, he makes sure the report is long enough to annoy the woman who assigned it. Their interaction after he is done giving his presentation leads him to coin the word "frindle," which means pen.
Nick says, "'From this day on and forever, I will never use the word pen again. Instead, I will use the word frindle, and I will do everything possible so others will, too.''
The word catches on in a big way. A local businessman hears about the commotion surrounding the creation of the word and starts selling Frindle-branded products, giving a cut of the profits to Nick. When Nick turns 21, he has access to enough money that he is able to donate one million dollars to the school where he created the word frindle.
He also receives a dictionary that has the word frindle in it. Nick has come full circle, from questioning where words come from to creating words of his own.