The term 'DIURNAL' is used to describe an organism or activity that is active during the daytime. This term is often used to refer to animals that are awake and active during the day, such as birds, reptiles, and some mammals. It can also be used to refer to activities that take place during the day, such as certain types of work or leisure activities. DIURNAL organisms and activities are in contrast to those that are nocturnal, which are active during the night.