9 Definitions

Effective 20 May 2019, the 144th anniversary of the Metre Convention, the SI base units were redefined in agreement with the International System of Quantities. In the redefinition, four of the seven SI base units – the kilogram, ampere, kelvin, and mole – were redefined by setting exact numerical values for the Planck constant, the elementary electric charge, the Boltzmann constant, and the Avogadro constant, respectively. The second, metre, and candela were already defined by physical constants and were not subject to correction to their definitions. The new definitions aimed to improve the SI without changing the value of any units, ensuring continuity with existing measurements. In November 2018, the 26th General Conference on Weights and Measures (CGPM) unanimously approved these changes, which the International Committee for Weights and Measures (CIPM) had proposed earlier that year after determining that previously agreed conditions for the change had been met. These conditions were satisfied by a series of experiments that measured the constants to high accuracy relative to the old SI definitions, and were the culmination of decades of research.

The Americas, also known as America, are lands of the Western Hemisphere, composed of numerous entities and regions variably defined by geography, politics, and culture.

This article describes several definitions of Palestinian.

A parlour is a reception room or public space. In medieval Christian Europe, the "outer parlour" was the room where the monks or nuns conducted business with those outside the monastery and the "inner parlour" was used for necessary conversation between resident members. In the English-speaking world of the 18th and 19th century, having a parlour room was evidence of social status.

The definition of planet, since the word was coined by the ancient Greeks, has included within its scope a wide range of celestial bodies. Greek astronomers employed the term asteres planetai, "wandering stars", for star-like objects which apparently moved over the sky. Over the millennia, the term has included a variety of different objects, from the Sun and the Moon to satellites and asteroids.

This article provides a list of definitions of the term pogrom. The term originated as a loanword from the Russian verb громи́ть, meaning "to destroy, to wreak havoc, to demolish violently". The events in Odessa during Holy Week in 1871 were the first to be widely called a "pogrom" in Russian, and the events of 1881–82 introduced the term into common usage throughout the world.

Historians have produced and worked with a number of definitions of Puritanism, in an unresolved debate on the nature of the Puritan movement of the 16th and 17th century. There are some historians who are prepared to reject the term for historical use. John Spurr argues that changes in the terms of membership of the Church of England, in 1604–6, 1626, 1662, and also 1689, led to re-definitions of the word "Puritan". Basil Hall, citing Richard Baxter. considers that "Puritan" dropped out of contemporary usage in 1642, with the outbreak of the First English Civil War, being replaced by more accurate religious terminology. Current literature on Puritanism supports two general points: Puritans were identifiable in terms of their general culture, by contemporaries, which changed over time; and they were not identified by theological views alone.

The definition of religion is a controversial and complicated subject in religious studies with scholars failing to agree on any one definition. Oxford Dictionaries defines religion as the belief in and worship of a superhuman controlling power, especially a personal God or gods. Others, such as Wilfred Cantwell Smith, have tried to correct a perceived Judeo-Christian and Western bias in the definition and study of religion. Thinkers such as Daniel Dubuisson have doubted that the term religion has any meaning outside of western cultures, while others, such as Ernst Feil even doubt that it has any specific, universal meaning even there.

There have been many attempts at defining science fiction. This is a list of definitions that have been offered by authors, editors, critics and fans over the years since science fiction became a genre. Definitions of related terms such as "science fantasy", "speculative fiction", and "fabulation" are included where they are intended as definitions of aspects of science fiction or because they illuminate related definitions—see e.g. Robert Scholes's definitions of "fabulation" and "structural fabulation" below. Some definitions of sub-types of science fiction are included, too; for example see David Ketterer's definition of "philosophically-oriented science fiction". In addition, some definitions are included that define, for example, a science fiction story, rather than science fiction itself, since these also illuminate an underlying definition of science fiction.