The crossword solution for the term 'prefix with region' is ECO. ECO is an abbreviation for the word 'ecology, ' which is the scientific study of the relationships between organisms and their environment. Ecology is a branch of biology that studies the interactions between living organisms and their environment, including the physical, chemical, and biological components of the environment. ECO is often used as a prefix to refer to regional or local environmental issues, such as eco-tourism or eco-friendly products.