Nocturnal means belonging to or active during the night, such as "nocturnal animals are active at night". AnswerParty!
The term behavioural sciences encompasses all the disciplines that explore the activities of and interactions among organisms in the natural world. It involves the systematic analysis and investigation of human and other animal behaviour through controlled and naturalistic observation, and disciplined scientific experimentation. It attempts to accomplish legitimate, objective conclusions through rigorous formulations and observation. Examples of behavioural sciences include social psychology, psychobiology, and sociology.
A circadian rhythm // is any biological process that displays an endogenous, entrainable oscillation of about 24 hours. These rhythms are driven by a circadian clock, and rhythms have been widely observed in plants, animals, fungi and cyanobacteria. The term circadian comes from the Latin circa, meaning "around" (or "approximately"), and diem or dies, meaning "day". The formal study of biological temporal rhythms, such as daily, tidal, weekly, seasonal, and annual rhythms, is called chronobiology. Although circadian rhythms are endogenous ("built-in", self-sustained), they are adjusted (entrained) to the local environment by external cues called zeitgebers, commonly the most important of which is daylight.
A nocturnal emission or wet dream is a type of spontaneous orgasm, involving either erection during sleep and/or ejaculation during sleep for a male, or lubrication of the vagina for a female. Nocturnal emissions are most common during adolescence and early young adult years, but they may happen any time after puberty. It is possible to wake up during a wet dream, or to simply sleep through it.