Which Words Spell “Almost Nilpotent?”

A class of words is introduced with the property that a finite group satisfying an identity of length N defined by a member of this class is nilpotent-of-N-bounded-class-by-N-bounded-exponent. Conversely, we see that this class of words characterises such groups; a group which is nilpotent-of-class-c-by-exponent-at-most-c, satisfies an identity from this class whose length is c-bounded. Related results are discussed.