Definition of diurnal

The word "diurnal" originates from the Latin word "diurnus," which means "daily" or "of the day." This Latin word is derived from the phrase "diu regnare," meaning "to reign for a day." In English, the word "diurnal" initially referred to a day or a period of 24 hours, particularly in relation to astronomical events. Over time, the meaning of "diurnal" expanded to include anything that occurs or is related to the daytime, such as diurnal animals, which are active mainly during the day. In modern English, "diurnal" is often used to describe habits, behaviors, or activities that occur daily or are characteristic of daytime. For example, a diurnal routine might refer to a daily schedule or a diurnal creature might be an animal that is active during the daytime.