The term 'change of form' can be described by the word 'METAMORPHOSIS', which has 13 letters. METAMORPHOSIS is a biological process in which an organism undergoes a transformation from one form to another, such as a caterpillar turning into a butterfly. This process is also seen in other organisms, such as frogs and salamanders, which undergo a transformation from a larval stage to an adult stage. METAMORPHOSIS is a natural process that occurs in many species, and it is an important part of the life cycle of many organisms.