[for.ma.tive] adj (15c) 1 a: giving or capable of giving form: constructive "a ~ influence" b: used in word formation or inflection
2: capable of alteration by growth and development; also: producing new cells and tissues
3: of, relating to, or characterized by formative effects or formation "~ years" -- for.ma.tive.ly adv
[2]formative n (1816): the element (as a suffix) in a word that serves to give the word appropriate form and is not part of the base