To be in another form' is a phrase that refers to the process of transformation. Transformation is the act of changing something from one form to another, such as a caterpillar transforming into a butterfly. The three letter answer to this crossword puzzle is 'ARE', which is the present tense conjugation of the verb 'to be'. This verb is used to describe the process of transformation, as in 'the caterpillar is transforming into a butterfly'.