The term 'PREFIX WITH MEDIA OR GRAIN' can be solved by the word 'MULTI, ' which is a five-letter prefix meaning 'MANY.' This prefix is often used in combination with other words to indicate a large number or variety of something. For example, 'multimedia' refers to a combination of different media forms, such as text, audio, and video, while 'multigrain' refers to a type of food made with multiple types of grain.