Wikipedia,

the free encyclopedia that anyone can edit.

Today's featured article

Example of a polynomial equation, studied in elementary algebra

Algebra is the branch of mathematics that studies certain abstract systems, known as algebraic structures, and the manipulation of statements within these systems. Elementary algebra generalizes arithmetic by using variables in addition to numbers. It covers methods of transforming equations to solve them by isolating variables. Linear algebra examines systems of several linear equations and techniques to determine for which values all equations in a system are true at the same time. Abstract algebra investigates algebraic structures, which consist of a set of objects together with operations defined on that set. It distinguishes algebraic structures, such as groups, rings, and fields, based on their number of operations and the laws they follow. Algebraic methods were first studied in ancient times to solve specific problems. As algebra evolved, it became increasingly abstract and generalized, leading to many applications in other branches of mathematics and the empirical sciences. (Full article...)

Recently featured:

Did you know ...

Carlyle Hotel

... that a staff member at the Carlyle Hotel (pictured) once lent his own bow tie to Laurence Olivier?
... that Yangginu plotted to defeat Khan Wan to avenge his murdered father?
... that to prepare for her role in The Last Dance, actress Michelle Wai learned to perform a Taoist funeral ritual traditionally performed only by men?
... that the city council of Hamtramck, led by Mayor Amer Ghalib, banned the pride flag from publicly owned flagpoles?
... that the death rate from adrenal crises can reach as high as 6 percent?
... that Shane Connolly has provided flowers for two royal weddings and the coronation of Charles III?
... that the Child Law Project reports on Ireland's child-care system?
... that U.S. Army chaplain Patrick Ryan celebrated a Mass of thanksgiving for 10,000 people after the liberation of Rome?
... that Perplexities after Escher, a composition for heckelphone, string quartet and double bass, is based on five graphic artworks by M. C. Escher?

In the news

Bashar al-Assad

Syrian rebel forces capture Damascus following multiple offensives as overthrown president Bashar al-Assad (pictured) flees to Russia.
Notre-Dame de Paris reopens following reconstruction after the 2019 fire.
The first round of the Romanian presidential election is annulled by the Constitutional Court following allegations of Russian electoral interference.
The French government, led by Michel Barnier, collapses following a vote of no confidence by the National Assembly.

On this day

December 12: Beginning of the Yule Lads' arrival in Iceland

George W. Bush

627 – At the Battle of Nineveh, the Byzantine army under Emperor Heraclius defeated the forces of Sasanian emperor Khosrow II, commanded by Rhahzadh, near present-day Mosul, Iraq.
1936 – Republic of China leader Chiang Kai-shek was kidnapped by Marshal Chang Hsueh-liang, a former warlord of Manchuria.
1988 – Three trains collided near Clapham Junction railway station in London, killing 35 people and injuring 484 others.
2000 – The U.S. Supreme Court ruled in Bush v. Gore that the recount of ballots cast in Florida for the presidential election be stopped, effectively making George W. Bush (pictured) the winner.
2021 – At the season-ending Abu Dhabi Grand Prix, Max Verstappen overtook Lewis Hamilton on the final lap to become World Drivers' Champion.

Geoffrey (d. 1212)
Edvard Munch (b. 1863)
Ikuhiko Hata (b. 1932)
Maʻafu Tukuiʻaulahi (d. 2021)

More anniversaries:

Today's featured picture

Marcelo Rebelo de Sousa (born 12 December 1948) is a Portuguese politician and academic. He has been the 20th and current president of Portugal since 9 March 2016. As a member of the Social Democratic Party, he previously served as a minister and parliamentarian in the Assembly of the Republic. This photograph of Rebelo de Sousa was taken in 2017 at Web Summit, an annual technology conference held in Lisbon.

Photograph credit: João Pedro Correia

Recently featured:

Other areas of Wikipedia

Community portal – The central hub for editors, with resources, links, tasks, and announcements.
Village pump – Forum for discussions about Wikipedia itself, including policies and technical issues.
Site news – Sources of news about Wikipedia and the broader Wikimedia movement.
Teahouse – Ask basic questions about using or editing Wikipedia.
Help desk – Ask questions about using or editing Wikipedia.
Reference desk – Ask research questions about encyclopedic topics.
Content portals – A unique way to navigate the encyclopedia.

Wikipedia's sister projects

Wikipedia is written by volunteer editors and hosted by the Wikimedia Foundation, a non-profit organization that also hosts a range of other volunteer projects: