4 (number)

Four redirects here. This article is relating to number 4. For the year, to see 4. ----

4 ( four ) is the Entier naturalness according to 3 and preceding 5. Four never takes S final except in the expression " between quatre' yeux".

The Préfixe of the international system for 1000⁴ is Téra (T), and for its reverse Pico (p).

Evolution of the glyphe

To account for 1,2 and 3 with as many bars as the figure represents was reasonable, but with 4, to write four features started to become tiring. The Indian Brahmane S simplified 4 by uniting its four lines in a cross which resembles our modern sign more . The Sungas and the other Hindu ones would have added an horizontal line to the top of the figure, Kshatrapa and Pallava improved it at the point where the speed of writing became correct. The Arab S did not have time to make the cursive whimsical ones: their 4 still has the primary education concept of the cross, but to preserve efficiency, they summarized it in a loop connecting the end of left with the end top; the end of right-hand side was supplemented of a curve. The Européens removed the final curve and made gradually the figure less cursive, while finishing with a Glyphe which could have been improved in a way much simpler than the upset road than it had taken: by taking the cross of the Brahmans simply and adding a line to connect the ends left and higher.

Current C-Ws communication

The C-W communication “4” is not only used in the world; a certain number of Alphabet S - particularly those of the languages of the Indian sub-continent and South-East Asia - use different C-Ws communication.

In mathematics

Four is smallest made up Nombre, its Diviseur S clean is 1 and 2. Four is also a highly made up Nombre. The highly made up number according to is Six. Four is the second square Nombre, the triangular second Nombre centered and the second powerful Nombre.

Four is an even number, it is also a tetrahedral Nombre.

Four is the only made up number which is equal to the nap of its factors first. Consequently of that, it is smallest Nombre of Smith.

It is also a Nombre of Motzkin.

$2 + 2 = 4 \,$ (addition)

2 \ times 2 = 4

(multiplication)

2^2 = 4 \,

(exponentiation)

By continuing the reason with the powers reiterated of Knuth:

2 \ uparrow \ uparrow 2 = 4

2 \ uparrow \ uparrow \ uparrow 2 = 4

and so on, for any number of $\ uparrow \,$ .

A figure planes of four east coasts a Quadrilatère, sometimes called in Greek form tetragonal . (particular cases: Trapezoid, Parallelogram, Rhombus, Right-angled, square).

A solid of four faces is a Tétraèdre. A regular tetrahedron is simplest of the solid of Plato. It can also be called one 3 - Simplexe, it has four triangular faces and four tops.

Smallest cyclic group not has four elements; it is the Groupe of Klein. Four is also the order of the more not-commonplace small groups which are not simple.

The Théorème of the four colors, shown in 1976 establishes that a planar Graphe (or, in an equivalent way, a chart punt with two-dimensions with areas, such as the countries) can be coloured while using with more the four colors, therefore the adjacent areas are always of different colors. Three colors are not, in general, sufficient to guarantee this.

The Théorème of the four squares of Joseph-Louis Lagrange establishes that each Integer positive can be written in the form of a sum of to the more four Carré S. Three are not always sufficient; 7 for example cannot be written like a sum of three squares.

Each divisible natural number by 4 is a difference in squares of two natural numbers, c.a.d. $4x = y^2 - z^2 \,$

Four is a Nombre Harshad complete and a number semi-méandrique.

In other fields

A quad is an interval of 4 notes in the range. It can be right (2 let us tons and half) or increased (3 let us tons, called also decreased fifth or triton ).

Four (furnace) is the only English number which, when it is spelled, has the same number of letters as what it names.

Four (四, writes formally: 肆, Pinyin si4) is regarded as a Nombre unlucky person in the cultures Chinese and the Japanese because it sounds like the “dead” word (死 Pinyin si3). Because of that, much of serial numbers the “four avoid”: c.a.d. that there does not exist series starting with the 4, for example: PDA S Palm, the plays Leisure Follows Larry, the cellphones Nokia etc

The four elements of traditional Greece are the fire, the Air, the Eau and the Ground.

Four is:

the number of marks in the charts of play (heart, square, spade and clover).
the number of the noble truths in the Buddhist belief.
In numerology, the 4 represents the Réalisation .
With the Japan, 4 is the figure of death, because of the similar pronunciation of the two ideograms.

See too

four|four

Fourth generation: 4G or G4

Morse code in which figure 4 is worth “**** -”
Combinaisons of figure-letter starting with 4:

4D 4G 4L 4R 4X

External bonds

Almanac and dictionary of the numbers (site of Gerard Villemin)

Zh-yue: 4

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