Formative/ˈfɔːrmətɪv/ Definition 1 of 3Pro Tip 1/2Shaping Influence Focuses on someone's contribution in developing others' characteristics or paths. Her mentor's advice was formative in shaping her career. Pro Tip 2/2Subtle Impact Refers to a less obvious but significant influence on development or decisions. The novel's themes had a formative effect on his worldview.