Final answer:
Assimilation is the term for the cognitive process in which existing knowledge structures are modified to fit new information.
Step-by-step explanation:
The cognitive process in which existing knowledge structures are modified so that new information can fit with what is known is called assimilation. Assimilation is a process described by Jean Piaget in his theory of cognitive development, where new information is incorporated into existing schemas or mental representations. It allows individuals to make sense of new experiences based on their existing knowledge.