Left–right political spectrum in the context of "Right-wing politics"

A spectrum (pl.: spectra or spectrums) is a set of related ideas, objects, or properties whose features overlap such that they blend to form a continuum. The word spectrum was first used scientifically in optics to describe the rainbow of colors in visible light after passing through a prism. In the optical spectrum, light wavelength is viewed as continuous, and spectral colors are seen to blend into one another smoothly when organized in order of their corresponding wavelengths. As scientific understanding of light advanced, the term came to apply to the entire electromagnetic spectrum, including radiation not visible to the human eye.

Spectrum has since been applied by analogy to topics outside optics. Thus, one might talk about the "spectrum of political opinion", or the "spectrum of activity" of a drug, or the "autism spectrum". In these uses, values within a spectrum may not be associated with precisely quantifiable numbers or definitions. Such uses imply a broad range of conditions or behaviors grouped together and studied under a single title for ease of discussion. Nonscientific uses of the term spectrum are sometimes misleading. For instance, a single left–right spectrum of political opinion does not capture the full range of people's political beliefs. Political scientists use a variety of biaxial and multiaxial systems to more accurately characterize political opinion.

Left-wing politics or leftism is the range of political ideologies that support and seek to achieve social equality and egalitarianism, often in opposition to social hierarchy either as a whole, or to certain social hierarchies. Left-wing politics typically involve a concern for those in society whom its adherents perceive as disadvantaged relative to others as well as a belief that there are unjustified inequalities that need to be reduced or abolished, through radical means that change the nature of the society they are implemented in. According to emeritus professor of economics Barry Clark, supporters of left-wing politics "claim that human development flourishes when individuals engage in cooperative, mutually respectful relations that can thrive only when excessive differences in status, power, and wealth are eliminated."

Within the left–right political spectrum, left and right were coined during the French Revolution, referring to the seating arrangement in the French National Assembly between revolutionaries and monarchists respectively. Usage of the term left became more prominent after the restoration of the French monarchy in 1815, when it was applied to the Independents. The word wing was first appended to left and right factions in the late 19th century, usually with disparaging intent, and left-wing was applied to those who were unorthodox in their religious or political views.

The Labour Party, commonly Labour, is one of the two main political parties in the United Kingdom, along with the Conservative Party. It sits on the centre-left of the left–right political spectrum, and has been described as an alliance of social democrats, democratic socialists and trade unionists. It has been the governing party since the 2024 general election. Keir Starmer has been Leader of the Labour Party since 2020 and Prime Minister of the United Kingdom since 2024. There have been twelve Labour governments and seven Labour prime ministers.

The Labour Party was founded in 1900, having emerged from the trade union movement and socialist parties of the 19th century. It was electorally weak before the First World War, but in the early 1920s overtook the Liberal Party to become the main opposition to the Conservative Party, and briefly formed a minority government under Ramsay MacDonald in 1924. In 1929 Labour for the first time became the largest party in the House of Commons, with 287 seats, but fell short of a majority, forming another minority government. In 1931, in response to the Great Depression, MacDonald formed a new government with Conservative and Liberal support, which led to his expulsion from the party. Labour was soundly defeated by his coalition in 1931, winning only 52 seats, but began to recover in 1935 with 154 seats.

The Conservative and Unionist Party, commonly the Conservative Party and colloquially the Tories, is one of the two main political parties in the United Kingdom, along with the Labour Party. It sits on the centre-right to right-wing of the left–right political spectrum. Following its defeat by Labour at the 2024 general election it is currently the second-largest party by the number of votes cast and number of seats in the House of Commons; as such it has the formal parliamentary role of His Majesty's Most Loyal Opposition. It encompasses various ideological factions including one-nation conservatives, Thatcherites and traditionalist conservatives. There have been 20 Conservative prime ministers.

The Conservative Party was founded in 1834 from the Tory Party and was one of two dominant political parties in the 19th century, along with the Liberal Party. Under Benjamin Disraeli it played a preeminent role in politics at the height of the British Empire. In 1912 the Liberal Unionist Party merged with the party to form the Conservative and Unionist Party. Its rivalry with the Labour Party has shaped modern British politics for the last century. David Cameron sought to modernise the party after his election as leader in 2005, and the party governed from 2010 to 2024 under five prime ministers, latterly Rishi Sunak.

Far-left politics encompasses a range of ideologies, such as anarchism, communism, Maoism, Leninism, Stalinism and Marxism, that are situated on the leftmost end of the political spectrum. The term is also used to describe various forms of authoritarianism and characterize groups that advocate revolutionary socialism, communist ideologies, anti-capitalism, anti-imperialism and anti-globalisation. Far-left terrorism consists of terrorism that is engaged in by extremist, militant, or insurgent groups that attempt to realize their ideals through political violence rather than democratic processes.

In politics, a reactionary is a person who favors a return to a previous state of society which they believe possessed positive characteristics absent from contemporary society. As a descriptor term, reactionary derives from the ideological context of the left–right political spectrum. As an adjective, the word reactionary describes points of view and policies meant to restore a status quo ante. As an ideology, reactionism is a tradition in right-wing politics; the reactionary stance opposes policies for the social transformation of society, whereas conservatives seek to preserve the socio-economic structure and order that exists in the present. A conservative might turn reactionary, when prioritizing older traditions over recently accepted ones. In popular usage, reactionary refers to a strong traditionalist conservative political perspective of a person opposed to social, political, and economic change. In the 20th century, reactionary politics was associated with restoring values such as discipline, hierarchy and respect for authority and privilege.

Reactionary ideologies can be radical in the sense of political extremism in service to re-establishing past conditions. To some writers, the term reactionary carries negative connotations—Peter King observed that it is "an unsought-for label, used as a torment rather than a badge of honor." Despite this, the descriptor "political reactionary" has been adopted by writers such as the Austrian monarchist Erik von Kuehnelt-Leddihn, the Scottish journalist Gerald Warner of Craigenmaddie, the Colombian political theologian Nicolás Gómez Dávila, and the American historian John Lukacs.