And now the willow - if it's dry, it is not kosher for the 4 minim, in the same formulation as the lulav and the hadas, which leads to defining what this "aravah, arvei nachal" is. Plus, how language changed, where names are confused or switched, and the change sticks. With possible implications in halakhah. Also, fulfilling the mitzvah of the 4 minim, according to an assortment of Tannaim, and to what extent the tops can be cut off, and why the etrog isn't bound with the others.