Formative is an adjective used to describe something that is in the process of being formed or developed. DEVELOPMENTAL (13 letters) refers to something that is related to the development of a person or thing, such as a child's development or the development of a new technology. IMPRESSIONABLE (14 letters) describes something that is easily influenced by external factors, such as a young child who is easily influenced by their parents. Seminal (7 letters) is used to describe something that is highly influential or important, such as a seminal work of literature or a seminal moment in history. PLASTIC (7 letters) is used to describe something that is malleable or able to be shaped, such as plasticine or a PLASTIC material. All of these words can be used to describe something that is formative.