A century is a period of 100 years. Centuries are numbered ordinally in English and many other languages. The word century comes from the Latin centum, meaning one hundred. Century is sometimes abbreviated as c.
A centenary is a hundredth anniversary, or a celebration of this, typically the remembrance of an event which took place a hundred years earlier.
Although a century can mean any arbitrary period of 100 years, there are two viewpoints on the nature of standard centuries. One is based on strict construction, while the other is based on popular perspective (general usage).
According to the strict construction of the Gregorian calendar, the 1st century AD began with 1 AD and ended with 100 AD, with the same pattern continuing onward. In this model, the n-th century started/will start on the year (100 × n) - 99 and ends in 100 × n. Because of this, a century will only include one year, the centennial year, that starts with the century's number (e.g. 1900 was the last year of the 19th century).
In general usage, centuries are built by grouping years based on their shared digits. In this model, the 'n' -th century started/will start on the year (100 x n) - 100 and ends in (100 x n) - 1. For example, the 20th century is generally regarded as from 1900 to 1999, inclusive. This is sometimes known as the odometer effect. The astronomical year numbering and ISO 8601 systems both contain a year zero, so the first century begins with the year zero, rather than the year one.
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Informally, years may be referred to in groups based on the hundreds part of the year. In this system, the years 1900-1999 are referred to as the nineteen hundreds (1900s). Aside from English usage, this system is used in Swedish, Danish, Norwegian, Icelandic, Finnish and Hungarian. The Swedish nittonhundratalet (or 1900-talet), Danish nittenhundredetallet (or 1900-tallet), Norwegian nittenhundretallet (or 1900-tallet), Finnish tuhatyhdeksänsataaluku (or 1900-luku) and Hungarian ezerkilencszázas évek (or 1900-as évek) refer unambiguously to the years 1900-1999.
Italian also has a quite similar alternative naming system but it only expresses the hundreds and omits the word for "thousand". This system mainly functions from the 11th to the 20th century:
Such Italian namings are borrowed in many other languages when referring to the history of Italy.
While the century has been commonly used in the West, other cultures and calendars have utilized differently sized groups of years in a similar manner. The Hindu calendar, in particular, summarizes its years into groups of 60, while the Aztec calendar considers groups of 52.