An infradian rhythm is a biological cycle that lasts longer than 24 hours. These rhythms can be observed in various organisms, including humans, and are often linked to physiological processes. A common example is the human menstrual cycle, which typically spans about 28 days. Infradian rhythms can influence behavior, hormone levels, and other bodily functions. They are important for regulating reproductive cycles and seasonal changes in some animals. Understanding these rhythms helps researchers study health patterns and the effects of environmental factors on living organisms.