An annual cycle refers to a set of changes or events that uniformly, or consistently, take place at the same time of year. In

biology Biology is the scientific study of life. It is a natural science with a broad scope but has several unifying themes that tie it together as a single, coherent field. For instance, all organisms are made up of cells that process hereditar ...

, the annual cycle for plants and animals details behavioral and chemical changes that take place as the seasons advance. In business, a

business cycle Business cycles are intervals of expansion followed by recession in economic activity. These changes have implications for the welfare of the broad population as well as for private institutions. Typically business cycles are measured by exami ...

refers to the way modelling and analysis is applied to the periodic development and marketing of new products and services. In

religion Religion is usually defined as a social- cultural system of designated behaviors and practices, morals, beliefs, worldviews, texts, sanctified places, prophecies, ethics, or organizations, that generally relates humanity to supernatural ...

, the annual cycle refers to the various celebrations or memorials that occur in the same sequence from year to year. For example, in

Christianity Christianity is an Abrahamic monotheistic religion based on the life and teachings of Jesus of Nazareth Jesus, likely from he, יֵשׁוּעַ, translit=Yēšūaʿ, label=Hebrew/Aramaic ( AD 30 or 33), also referred to as Jesu ...

the liturgical year is an annual cycle, which for some Christian denominations is composed of the ''temporal cycle'' that tracks the events in the life of

Christ Jesus, likely from he, יֵשׁוּעַ, translit=Yēšūaʿ, label= Hebrew/Aramaic ( AD 30 or 33), also referred to as Jesus Christ or Jesus of Nazareth (among other names and titles), was a first-century Jewish preacher and religi ...

, and the ''sanctoral cycle'' which tracks the various saint's days. Some Christian churches only observe the ''temporal cycle''.Flesher, Pau
"Christian Time and Worship"
''Exploring Religions'' University of Wyoming In

climatology Climatology (from Ancient Greek, Greek , ''klima'', "place, zone"; and , ''wiktionary:-logia, -logia'') or climate science is the scientific study of Earth's climate, typically defined as weather conditions averaged over a period of at least 30 ...

, an annual cycle is the part of a measured quantity's fluctuation that is attributed to Earth's changing position in orbit over the course of the year. Such quantities might be influenced directly (e.g. incoming solar radiation at a point at the surface) or indirectly (e.g.

stratospheric The stratosphere () is the second layer of the atmosphere of the Earth, located above the troposphere and below the mesosphere. The stratosphere is an atmospheric layer composed of stratified temperature layers, with the warm layers of air hi ...

westerlies and easterlies over the winter and summer hemispheres, respectively) by orbital position. Mathematically, the climatological annual cycle is commonly estimated from observational data or model output by taking the average of all Januaries, all Februaries, and so forth. If the observational record is long enough and conditions are stationary (i.e. there is no significant long-term trend), a meaningful annual cycle will result that can be used to calculate an anomaly time series.

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Earth sciences {{climate-stub