3 (number)

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This article discusses the number three. For the year AD 3, see 3. For other uses of 3, see 3 (disambiguation)

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Cardinal	3 three
Ordinal	3rd third
Numeral system	ternary
Factorization	prime
Divisors	1, 3
Roman numeral	III
Roman numeral (Unicode)	Ⅲ, ⅲ
prefixes	tri- (from Greek) tre-/ter- (from Latin)
Binary	11
Octal	3
Duodecimal	3
Hexadecimal	3
Hebrew	ג (Gimel)
Arabic	٣

Look up three in
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3 (three) is a number, numeral, and glyph. It is the natural number following 2 and preceding 4.

[edit] In mathematics

Three is the first odd prime number, and the second smallest prime after two. It is both the first Fermat prime (2^2º + 1) and the first Mersenne prime (2² - 1), as well as the first lucky prime. However, it's the second Sophie Germain prime, the second Mersenne prime exponent, the second factorial prime (2! + 1), the second Lucas prime, the second Stern prime.

Three is the first unique prime due to the properties of its reciprocal.

Three is the second triangular number and it is the only prime triangular number. Three is the only prime which is one less than a perfect square. Any other number which is one less than a perfect square will be the product of the numbers one more than, and one less than, the square root of said square.

Three non-collinear points determine a plane and a circle.

Three is the fourth Fibonacci number and the third that is unique. In the Perrin sequence, however, 3 is both the zeroeth and third Perrin numbers.

Three is the fourth open meandric number.

Vulgar fractions with 3 in the denominator have a single digit repeating sequences in their decimal expansions, (.000..., .333..., .666..., .999...)

A natural number is divisible by three if the sum of its digits in base 10 is divisible by 3. For example, the number 21 is divisible by three (3 times 7) and the sum of its digits is 2 + 1 = 3. Because of this, the reverse of any number that is divisible by three (or indeed, any permutation of its digits) is also divisible by three. For instance, 1368 and its reverse 8631 are both divisible by three (and so are 1386, 3168, 3186, 3618, etc..). See also Divisibility rule.

A triangle is the most durable shape possible, the only "perfect" figure which if all endpoints have hinges will never change its shape unless the sides themselves are bent.

3 is the only integer between e and π.

[edit] In numeral systems

Base	Numeral system
2	binary	11
3	ternary	10
over 3 (decimal, hexadecimal)		3

[edit] List of basic calculations

Multiplication	1	2	3	4	5	6	7	8	9	10		11	12	13	14	15	16	17	18	19	20		21	22	23	24	25		50	100	1000
$3 \times x$	3	6	9	12	15	18	21	24	27	30		33	36	39	42	45	48	51	54	57	60		63	66	69	72	75		150	300	3000

Division	1	2	3	4	5	6	7	8	9	10		11	12	13	14	15
$3 \div x$	3	1.5	1	0.75	0.6	0.5	$0.\overline{4}2857\overline{1}$	0.375	$0.\overline{3}$	0.3		$0.\overline{2}\overline{7}$	0.25	$0.\overline{2}3076\overline{9}$	$0.2\overline{1}4285\overline{7}$	0.2
$x \div 3$	$0.\overline{3}$	$0.\overline{6}$	1	$1.\overline{3}$	$1.\overline{6}$	2	$2.\overline{3}$	$2.\overline{6}$	3	$3.\overline{3}$		$3.\overline{6}$	4	$4.\overline{3}$	$4.\overline{6}$	5

Exponentiation	1	2	3	4	5	6	7	8	9	10		11	12	13
$3 ^ x\,$	3	9	27	81	243	729	2187	6561	19683	59049		177147	531441	1594323
$x ^ 3\,$	1	8	27	64	125	216	343	512	729	1000		1331	1728	2197

[edit] Evolution of the glyph

Three is often the largest number written with as many lines as the number represents. The Romans tired of writing 4 as IIII, but to this day 3 is written as three lines in Roman and Chinese numerals. This was the way the Brahmin Indians wrote it, and the Gupta made the three lines more curved. The Nagari started rotating the lines clockwise and ending each line with a slight downward stroke on the right. Eventually they made these strokes connect with the lines below, and evolved it to a character that looks very much like a modern 3 with an extra stroke at the bottom. It was the Western Ghubar Arabs who finally eliminated the extra stroke and created our modern 3. (The "extra" stroke, however, was very important to the Eastern Arabs, and they made it much larger, while rotating the strokes above to lie along a horizontal axis, and to this day Eastern Arabs write a 3 that looks like a mirrored 7 with ridges on its top line): ٣

In fonts with text figures, 3 usually has a descender, for example, , though in some French fonts it has an ascender instead of a descender.

[edit] Pointed version

A common variant of the digit 3 has a pointed top, similar to the character ezh, sometimes used to prevent people from falsifying a 3 into an 8.

[edit] In science

White light is composed of the mixture of the three additive primary hues: red, green, and blue.
Triceratops had three horns.

[edit] Astronomy

There are three types of galaxies.
Globular Cluster M3 (also known as Messier Object 3 or NGC 5272) is a globular cluster in the Canes Venatici constellation.
The Roman numeral III stands for giant in the Yerkes spectral classification scheme.
The Roman numeral III (usually) stands for the third-discovered satellite of a planet or minor planet (e.g. Pluto III)

[edit] Chemistry

Three is the atomic number of lithium.
There are three basic states: liquid, solid, and gas

[edit] Physics

There are three generations of fundamental leptons (electron, muon, tauon and their neutrinos) and three groups of flavours of quarks (up-down, charmed-strange, top-bottom).

[edit] In religion

[edit] Abrahamic religions

There are three main Abrahamic religions: Judaism, Christianity and Islam.
The Holy Trinity in Christian doctrine (or trinity in general), is God both as a single entity and as three entities: the Father, the Son and the Spirit. This is also known as Tripartite division.
The Wise Men who visited Jesus after His birth left Him three gifts
A devout Muslim tries to make a pilgrimage to all three holy cities in Islam: Mecca, Medina, and Jerusalem
King Solomon states in Ecclesiastes 4:12: "A three-ply cord is not easily severed." Examples of this concept of three-ness in Judaism are:

The three Patriarchs: Abraham, Isaac, and Jacob
The three pilgrim festivals (Sheloshet HaRegalim): Passover, Shavuot, and Sukkot
The three leaders of the Jewish nation during their 40 years of wandering in the desert: Moses, Aaron, and Miriam
The Tanakh is comprised of 3 sections: Torah, Nevi'im, and Ketuvim
There are 3 daily prayer services: Shacharit, Mincha, and Maariv
There are three divisions of Jews: Kohen, Levi, and Israel
Shimon Hatzaddik taught: "On three things the world stands: On Torah, on prayer, and on acts of kindness" (Pirkei Avoth 1:2). Rabban Shimon ben Gamliel taught: "The world continues to exist because of three things: justice, truth, and peace" (ibid. 1:18)

Hamantaschen, a filled cookie served on Purim, has 3 corners which represent the biblical Haman's ears or his pockets.
The three Theological virtues referred to 1 Corinthians 13.
In Roman Catholicism, three groups of martyrs, collectively known as Faith, Hope, and Charity (named after the Theological Virtues).
Heaven, Hell and Purgatory (or Limbo).

[edit] Other religions

The Wiccan Rule of Three.
Robert Graves's Triple Goddess: Maiden, Mother, Crone.
In Taoism, the Three Pure Ones.
The three Gunas underlie action, in the Vedic system of knowledge. There is also the concept of Trimurti in Hindu tradition.The Buddha has three bodies.The three Vedas are called trayi i.e triad. Lord Shiva is Trinetra-Three-eyed. The confluence of the Ganga, Yamuna and hidden Sarasvati is the famous Triveni-confluence of three rivers.Buddhism's three refuges are Trisharana- Buddhan sharanam gacchami, Dhammam sharanam gacchami, Sangham sharanam gacchami.
In Greek mythology, the Three Graces or Charites. Also the number of heads of Cerberus, the monstrous dog that guards the gate to Hades
Various Triple deities.

[edit] In esoteric tradition

The Theosophical Society has three conditions of membership.
Gurdjieff's Three Centers and the Law of Three.
Aleister Crowley's model of the three schools of magick (Black, White and Yellow) from his Magick Without Tears.
Feri Tradition teaches of the existence of three souls in each individual person.

[edit] In philosophy

Plato split his utopian city into three populations: laborers, guardians (warriors), and philosophers (rulers)
Further, Plato split the soul into three parts: the appetitive, the spirted, and the rational
Hegel's dialectic of Thesis + Antithesis = Synthesis creates three-ness from two-ness.
The three Doshas (weaknesses) and their antidotes are the basis of Ayurvedic medicine in India.
Charles Sanders Peirce stipulated a triadic relation of interpretant, representamen, and object to explain the phenomenon of semeiosis.

[edit] As a lucky or unlucky number

Three (三, formal writing: 叁, pinyin san1, Cantonese: saam1) is considered a good number in Chinese culture because it sounds like the word "alive" (生 pinyin sheng1, Cantonese: saang1), compared to four (四, pinyin: si4, Cantonese: sei3) that sounds like the word "death" (死 pinyin si3, Cantonese: sei2).

Counting to three is common in situations where a group of people wish to perform an action in synchrony: Now, on the count of three, everybody pull! Assuming the counter is proceeding at a uniform rate, the first two counts are necessary to establish the rate, but then everyone can predict when "three" will come based on "one" and "two"; this is likely why three is used instead of some other number.

In Vietnam, it is bad luck to take a photo with three people in it.

Luck, especially bad luck, is often said to "come in threes".

Some cultures in history have a place for people of third gender.

[edit] In technology

On computer keyboards, the "3" key may be used to type the pound sign.
On most telephone keypads, the "3" key is also associated with the letters "D", "E", and "F".
In ASCII, the code for "3" in hexadecimal is 33. This is the only character in ASCII such that a large file consisting of a single character has identical-looking hexadecimal and normal representation.
The glyph "3" may be used as a subsitute for yogh (ȝ) when that character is not available.
Three is the minimum odd number of voting components for simple easy redundancy checks by direct comparison.
Three is approximately pi (actually closer to 3.14159) when doing rapid engineering wags or estimates. The same is true if one wants a rough-and-ready estimate of e, which is actually approximately 2.7183.
Some computer users may use "3" as an alternate to the letter "E", often in jest or to prevent search engines from reading their messages. This form of code is an example of basic Leetspeak.

[edit] In music

In music, the Roman numeral iii is the mediant scale degree, chord, or diatonic function, when distinguished III = major and iii = minor.

Three is the number of performers in a trio.

The 3/4 time signature of Western classical music tradition (Three beats to a measure, with the quarter note comprising the beat.) is said to represent the Holy Trinity of Christian doctrine, Father, Son and Holy Spirit. It is for this reason that it is often utilized in compositions which were written for use in ecclesiastical rites, or that are inspired by scriptural/spiritual themes and texts.

[edit] In filmography

Three is the title of a 2005 film, directed by Stewart Raffill, about the complex relations of beautiful woman (Kelly Brook) and two men (Billy Zane and Juan Pablo Di Pace) that are shipwrecked and trying to survive in an Island after a yachting accident.

[edit] In sports

In rugby union, 3 is the jersey number of the starting tighthead prop. It is also the number of points received for a successful drop goal or penalty kick.
In baseball, 3 is the number of strikes before the batter is out and the number of outs per side per inning. It also represents the first baseman's position. The number 3 position in the batting order is generally occupied by the team's best hitter. Alan Trammel, Gary Sheffield, and Babe Ruth, widely regarded as the greatest player in baseball history, all wore the number 3.
In basketball, a shot made from behind the three-point arc is worth 3 points. 3 is used to represent the small forward position.
Retired number of former baseball players Babe Ruth, Joe Medwick, Bill Terry, Harmon Killebrew, and Dale Murphy.
Is the number of the famous NASCAR stock car that Dale Earnhardt drove for nearly 20 years before his death in 2001. He won 6 out of his 7 championships while driving the #3 car. No one has driven the 3 car since his death.
In American football, 3rd down is the do or die down. If insufficient yardage is gained to achieve a first down, which starts a new series of downs, then coach/quarterback/coach in charge (CIC)/team is faced with fourth down: Shall we attempt immediate success and risk failure and giving other side good field position ... or punt to establish good defensive position while other side is on offensive?
In both American and Canadian football, the number of points received for a successful field goal.
In Canadian football, the last down before a team loses possession on downs. Usually, a team faced with a third down will punt (if far from the opponent's goal line) or attempt a field goal (if relatively close).
An Ironman triathlon consists of three events, a 2.4 mile (3.86 kilometer) swim, a 112 mile (180.2 kilometer) bike ride, and a 26.2 mile (42.2 kilometer) marathon run.

[edit] In other fields

International maritime signal flag for 3

For other uses and related terms, see also 3 (disambiguation) Three is:

Three is a mobile phone operator.
The number of stars in "Pacific's triple star" in the God Defend New Zealand, one of New Zealand's two national anthems.
The "third way" is a political term applied to a variety of "third choice" options that some offer as an alternative to dichotomous situations which may otherwise appear polarized.
The phrase "Third time's the charm" (or, rarely, "Three time's the charm") usually means that the third time a person attempts something, he or she will succeed
Three-bean salad is an appetizer containing three types of beans, such as kidney, yellow, and green beans
The television VHF channel most often used for hooking up VCRs and/or video game systems. If it is otherwise occupied by a local broadcaster, then channel 4 is used instead.
On most phones, the 3 key is associated with the letters D, E, and F, but on the BlackBerry it is the key for U and I.
"In Memory of 3" - a phrase about NASCAR driver Dale Earnhardt, who drove the number 3 car. It can also refer to a 2004 ESPN television movie about Earnhardt's life called, 3: The Dale Earnhardt Story.
No. 3 - 1997 Korean gangster comedy written and directed by Neung-han Song
In Astrology, Gemini is the 3rd astrological sign of the Zodiac.
The number 3 is often used as a literary device to provoke a feeling of unnaturalness, as twos are much more common in nature (limbs, hemispheres, eyes, etc). This is a prevailing theme in Ray Bradbury's novel Fahrenheit 451. The aliens and their machines in the 2005 film War of the Worlds were associated with features recurring in threes: eyes, legs, fingers, etc, for this same reason.
3 is the number of novels or films in a trilogy(such as 'The Lord of the Rings') and the number of interconnected works of art in a triptych
3 is the amount of sister needed to make up the 'charmed ones' from WB's television show 'charmed.' Without 3 witches the charmed ones, or the most powerful witches in time, could not exist.
In the massive multiplayer online role-playing game RuneScape, 3 is the lowest possible combat level attainable for a player.

LAZIO 3 - riomma 0

[edit] Historical years

3 A.D., 3 B.C., 1903, 2003, etc.

[edit] External links

Retrieved from "http://en.wikipedia.org../../../3/_/%28/3_%28number%29.html"

Categories: Numbers in pop culture | Integers

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