Convertible
CONVERTIBLE, adjective
1. That may be changed; susceptible of change; transmutable; transformable.
Minerals are not convertible into another species, though of the same genus.
2. So much alike that one may be used for another. Usury and interest are not now convertible terms, though formerly they were.
3. That may be changed, as one letter for another; as b, p and f are convertible letters.