Organisms that are active at night are referred to as what?

Organisms that are active at night are referred to as nocturnal. This term specifically describes species that have adapted their behaviors to be primarily active after sunset and through the night. Nocturnal animals often have specialized adaptations, such as enhanced night vision or sensitivity to sound, which help them thrive in low-light conditions. This evolutionary strategy allows them to avoid predators, hunt more effectively, or conserve water by minimizing exposure to the heat of the day.

In contrast, diurnal species are active during the day and typically rest at night. Crepuscular organisms are active during twilight hours, which include dawn and dusk. The term "active" is too broad and does not specify the time of activity relative to the day-night cycle. Thus, nocturnal is the most precise classification for organisms that exhibit nighttime activity.