Bats, scorpions, cockroaches, mice and certain types of rats have something in common besides being nasty animals that people often avoid. They actually are all nocturnal. This means that they are awake and active during the night instead of during the day. Diurnal is a term used to describe things that take place every day. In other words, they are things that happen each and every day.
For instance, usually, eating a meal is something that would be considered diurnal because it is something that happens each and every day. Therefore, the difference between nocturnal and diurnal are that they are opposite in meanings. Nocturnal happens at night whereas diurnal happens each day. Diurnal is usually used to describe events and nocturnal describes animals a lot.