Can you think of five four-letter words, each beginning with NE?
Sounds simple, however you cannot use a letter more than once, and you can’t re-use the N or the E anywhere else. So for instance, NELL is not allowed, as it has two Ls, NEON is not allowed as it repeats the N, and you cannot have both NETS and NEAT, as both have a T, but either word is acceptable on its own.