The crossword solution for the term 'prefix with night or day' is MID. The prefix MID is derived from the Old English word 'midd', meaning middle. It is used to indicate something that is in the middle of two other things, such as night and day. MID is often used to describe something that occurs between two points in time, such as midday or midnight. It can also be used to refer to a location that is halfway between two places, such as the midpoint of a journey.