Recently the leader of the choir in a small church learned firsthand how much difference one letter in a word can make when he spotted in the church bulletin this notice: "The choir director invites any members of the congregation who enjoy sinning to join the choir." In the culinary world one letter can also make a big difference. Take, for example, the distinction between macaroon and macaron . Though identical words except for one extra letter "o," the confections they refer to couldn't be