Cycle is a word originating from the Greek term kýklos, which means a series of cyclic phenomena, that is, that renew themselves constantly.
In the context of astronomy, a cycle is the time in years in which the same astronomical phenomena are repeated. We have the example of solar cycle, which lasts for 28 years and is not related to the movement of the Sun. At the end of this cycle, the days of the week correspond to the same dates of the month in which the cycle started.
On the other hand, the lunar cycle (or Meton cycle) lasts for 19 years or 235 months, after which the phases of the Moon repeat on approximately the same days, in the same order. The error in determining this cycle can be one or two days, due to the irregularity of the Moon's movement and the existence of a different number of leap years during the cycle. This cycle was discovered in 423 a. Ç. by the Greek astronomer Meton.
At biology, the cycle refers to the evolution of a living being, and each phase of its evolution. The evolutionary cycle is a phenomenon in which morphologically distinct phases are often repeated cyclically, from one generation to the next.
Within the scope of economy, an economic cycle is the time between two economic crises.
menstrual cycle
A woman's menstrual cycle is the time that elapses between the first day of a period and the first day of the next period and is intended for sexual reproduction and fertilization... It is a cycle controlled by a set of hormones, which prepare the woman's body for a possible pregnancy. In the case of a woman, the menstrual cycle considered "normal" can last between 21 and 35 days.
The menstrual cycle is composed of several phases: menstruation, proliferative phase, ovulation, luteal phase, ischemic phase, follicular phase. In women, menopause designates the end of menstrual cycles.
In other living beings, the variation that occurs periodically and regularly in the disposition of fertilization is known as estrous cycle.
water cycle
The water cycle is the transition of water between seas and continents. This cycle results from the evaporation, of the rains It's from surface runoff, which happen continuously.
This phenomenon occurs in two phases: an interior one (which originates the sources, thanks to the water circulation inside the terrestrial globe), and an exterior one (water circulation that occurs in the atmosphere). The water cycle can be divided into many other cycles, a larger one (outer phase) and a few smaller ones (phase interior), when evaporation and "precipitation" occur in isolation over the sea or over the continents.
oxygen cycle
This phenomenon is related to the carbon cycle. The oxygen cycle consists of the exchange of oxygen between photosynthetic and heterotrophic organisms. The vast majority of photosynthetic beings produce oxygen, which is used in the oxidation of compounds reduced by heterotrophic organisms.
Krebs Cycle
Also known as the tricarboxylic acid cycle, or citric acid cycle, the cycle of Krebs is an important process in the phenomenon of cell respiration, important for obtaining energy. It occurs in the mitochondria, and consists of one of the steps in the metabolism of aerobic organisms.
