4 (number)

natural number

In geometry, a square is a regular quadrilateral. It has four straight sides of equal length and four equal angles. Squares are special cases of rectangles, which have four equal angles, and of rhombuses, which have four equal sides. As with all rectangles, a square's angles are right angles (90 degrees, or Pi|/2 radians), making adjacent sides perpendicular. The area of a square is the side length multiplied by itself, and so in algebra, multiplying a number by itself is called squaring.

In geometry, a quadrilateral is a four-sided polygon, having four edges (sides) and four corners (vertices). The word is derived from the Latin words quadri, a variant of four, and latus, meaning "side". It is also called a tetragon, derived from Greek "tetra" meaning "four" and "gon" meaning "corner" or "angle", in analogy to other polygons (e.g. pentagon). Since "gon" means "angle", it is analogously called a quadrangle, or 4-angle. A quadrilateral with vertices A, B, C and D is sometimes denoted as \square ABCD.

geometric space with four dimensions

thumb|upright=1.0|For most medieval scholars, who believed that God created the universe according to geometric and harmonic principles, [[science—particularly geometry and astronomy—was linked directly to the divine. To seek these principles, therefore, would be to seek God.]]

a variation/mutation of the common clover, rare and said to bring good luck

In statistics, quartiles are a type of quantiles which divide the number of data points into four parts, or quarters, of more-or-less equal size. The data must be ordered from smallest to largest to compute quartiles; as such, quartiles are a form of order statistic. The three quartiles, resulting in four data divisions, are as follows: thumb|Q1, Median and Q3 The first quartile (Q1) is defined as the 25th percentile, where the lowest 25% data lies below this point. It is also known as the lower quartile. The second quartile (Q2) is the median of a data set; thus 50% of the data lies below t

numeral system with four as its base

proposed international order policed by the Americans, British, Soviets, and Chinese

four adjectives—"one, holy, catholic and apostolic"—attributed to the Church according to the Nicene-Constantinopolitan Creed

thumb|The zebra is a quadruped.

Deng Xiaoping's campaigns to modernize China

fictional character from Doctor Who

elements of Chinese culture (Old Ideas, Old Culture, Old Habits, Old Customs) purged during Mao’s Cultural Revolution

1815 alliance between Austria, Prussia, Russia, and the UK

four kingdoms which, according to the Book of Daniel, precede the "end-time" and the "Kingdom of God"

last four teams remaining in a play-off tournament

in Christian eschatology, Death, Judgment, Heaven, and Hell, the four last stages of the soul in life and the afterlife, often commended as a collective topic for pious meditation

infinite series

four bodies of water that metaphorically made up the boundaries of ancient China: Qinghai Lake (west), East China Sea (east), Lake Baikal (north) and South China Sea (south)

group of diseases caused by pollution in Japan

16th century division of the world into four continents; Africa, America, Asia and Europe

attempt to demonstrate the 4th dimension in visual arts

Catuṣkoṭi (Sanskrit; Devanagari: चतुष्कोटि, , Sinhalese:චතුස්කෝටිකය) refers to logical argument(s) of a 'suite of four discrete functions' or 'an indivisible quaternity' that has multiple applications and has been important in the Indian logic and the Buddhist logico-epistemological traditions, particularly those of the Madhyamaka school.

grammatical number indicating four items