What is (a) That which serves merely to give form, and is no part of the radical, as the prefix or the termination of a word. (b) A word formed in accordance with some rule or usage, as from a root called?

formative — (a) That which serves merely to give form, and is no part of the radical, as the prefix or the termination of a word. (b) A word formed in accordance with some rule or usage, as from a root. (Webster's 1913.)