9 (nine) is the natural number following 8 and preceding 10. The ordinal adjective is ninth.

Mathematics

Nine is a composite number, its proper divisors being 1 and 3. It is 3 times 3 and hence the third square number. 9 is a Motzkin number. It is the first composite lucky number.

Nine is the highest single-digit number in the decimal system. It is the second non-unitary square prime of the form (p²) and the first that is odd. All subsequent squares of this form are odd. It has a unique aliquot sum 4 which is itself a square prime. 9 is; and can be, the only square prime with an aliquot sum of the same form. The aliquot sequence of 9 has 5 members (9,4,3,1,0) this number being the second composite member of the 3-aliquot tree.

Religion and philosophy

• Nine, as the highest single-digit number (in base ten), symbolizes completeness in the Bahá'í Faith. In addition, the word Bahá' in the Abjad notation has a value of 9, and a 9-pointed star is used to symbolize the religion.
• The number 9 is revered in Hinduism and considered a complete, perfected and divine number because it represents the end of a cycle in the decimal system, which originated from the Indian subcontinent as early as 3000 BC.
• Important Buddhist rituals usually involve nine monks.
• The first nine days of the Hebrew month of Av are collectively known as "The Nine Days" (Tisha HaYamim), and are a period of semi-mourning leading up to Tisha B'Av, the ninth day of Av on which both Temples in Jerusalem were destroyed.
• Nine is a significant number in Norse Mythology. Odin hung himself on an ash tree for nine days to learn the runes.
• The Fourth Way Enneagram is one system of knowledge which shows the correspondence between the 9 integers and the circle.
• In the Christian angelic hierarchy there are 9 choirs of angels.
• Anton LaVey applied the number to Satan.
• Ramadan, the month of fasting and prayer, is the ninth month of the Islamic calendar.
• In many south Asian countries, the number nine is said to be a Kannan (Mannish-Woman) number which means it represents men who are womanly or act womanly, it is also synonymous for Pons.^{[citation needed]}

Chinese culture

• Nine (九 pinyin jiǔ) is considered a good number in Chinese culture because it sounds the same as the word "longlasting" (久 pinyin jiǔ)^{[citation needed]}.

• Nine is strongly associated with the Chinese dragon, a symbol of magic and power. There are nine forms of the dragon, it is described in terms of nine attributes, and it has nine children It has 9×13 scales, 9×9 being yang (masculine, or bad influence) and 9×4 being yin (feminine, or good influence).^[7]

• The dragon often symbolizes the Emperor, and the number nine can be found in many ornaments in the Forbidden City.

• The circular altar platform (Earthly Mount) of the Temple of Heaven has one circular marble plate in the center, surrounded by a ring of nine plates, then by a ring of 18 plates, and so on, for a total of nine rings, with the outermost having 81=9×9 plates.

• The name of the area called Kowloon in Hong Kong literally means: nine dragons.

• The nine-rank system was a civil service nomination system used during certain Chinese dynasties.

Sports

• Nine ball is the standard professional pocket billiards variant played in the United States.
• In association football (soccer) the centre-forward/striker traditionally (since at least the fifties) wears the number 9 shirt.
• The car number of the 1988 NASCAR Nextel Cup championship-winning team, when Bill Elliott won the title. He used this number again from 2001 to 2003. Kasey Kahne has driven the 9 car since 2004.
• In baseball, nine represents the right fielder's position.
• The retired uniform numbers of former baseball players Ted Williams and Roger Maris. Reggie Jackson also wore 9 with the Oakland A's for nine years and is now retired.
• The number of innings in a regulation, non-tied game of baseball
• The San Francisco 49ers are sometimes referred to as the "niners".
• The number worn by Roy Hobbs in the movie The Natural.
• In rugby union, the number generally worn by the scrum half.
• In rugby league, the number generally worn by the hooker.
• Nine Men’s Morris is a European board game known since Roman times.
• In professional ice hockey, number 9 is perhaps best known as the jersey number of Adam Graves, Bobby Hull,Gordie Howe and Maurice Richard, and the number has been retired in their honour by the New York Rangers, Chicago Blackhawks, Detroit Red Wings and Montreal Canadiens, respectively.

Technology

• ISO 9 is the ISO's standard for the transliteration of Cyrillic characters into Latin characters
• In the Rich Text Format specification, 9 is the language code for the English language. All codes for regional variants of English are congruent to 9 mod 256.
• The seven-segment display allows the number 9 to be constructed two ways, either with a hook at the end of its stem or without one. Most LCD calculators use the former, but some VFD models use the latter.
• The9 Limited (owner of the9.com) is a company in the video-game game industry, including former ties to the extremely popular MMORPG World of Warcraft

Companies

• Channel 9, an Australian free-to-air television station.
• Nine Lives Cat Food got its name from the legend that a cat has nine lives.
• Nine West is a brand for clothing.
• Number (n)ine is an avant garde japanese fashion label.

Music

• There is a rapper named Tech N9ne whose name stands for "Tech Nine" because 9 is the number of completion
• In music theory a ninth is the ninth note of a musical scale or the interval between the first note and the ninth. A ninth chord is a chord with a ninth
• In classical music the curse of the ninth refers to the superstition that a composer who writes a ninth symphony will die soon. Beethoven, who left his Tenth Symphony unfinished, is regarded by the superstition as the first victim of the curse. Among nineteenth-century Viennese composers, neither Franz Schubert nor Anton Bruckner finished nine symphonies. Gustav Mahler attempted to avoid the curse by naming the work after his Eighth symphony Das Lied von der Erde He then wrote a complete Ninth Symphony, yet his Tenth was unfinished at his death
• Bands with the number nine in their name include Sound Tribe Sector 9, Nine, Stroke 9, Nine Days, Nine Inch Nails, Nine Black Alps and Alice Nine.
• The Beatles released a song called "Revolution 9" which appears on The White Album (more properly known as The Beatles); its principal vocal feature is a voice repeating, "Number nine...number nine...number nine..." John Lennon, the primary composer of "Revolution 9", also released a solo recording entitled "#9 Dream. Also, George Harrison released a solo recording and a song both called "Cloud Nine"".
• "Love Potion No. 9 originally performed by The Clovers in 1955. Love Potion No. 9 was a 1992 movie starring Sandra Bullock and Tate Donovan.
• The first single of Leeds-based band ¡Forward, Russia! was called Nine and was released in April 2005. The title did not carry any symbolism, but followed the then "tradition" of the band for naming their songs in the order in which they were written.
• Composer Maury Yeston adapted Federico Fellini's 8½ for Broadway as the musical Nine, which won several Tony Awards in 1982, and was successfully revived in 2003 starring Antonio Banderas
• 9 is also the name of various albums, including 9 by Mercyful Fate, released in 1999, and 9 by Public Image Limited. Fairport Convention also released an album with the number for a title. Irish singer/songwriter Damien Rice released an album called 9 in November 2006
• In hip-hop, the rapper Nine
• "Nine" is a song title on the Neurosis album Given to the Rising
• Cloud Number Nine is a popular song by Canadian rock artist Bryan Adams
• In the American western folk ballad Oh My Darling, Clementine, Clementine's 'shoes were number nine'

Film and Television

• 9 is a 2009 film directed by Shane Acker, adapted from his short film of the same name
• Nine is a baseball manga series by Mitsuru Adachi
• Nine was the number of hostages in the TV show The Nine
• The Nines is a 2007 film directed by John August
• The Nine Network is an Australian television station
• District 9 is a 2009 science fiction film directed by Neill Blomkamp
• K-9, or K9, is the name of the robotic dog in the British science fiction television series Doctor Who, and its spin-off series The Sarah Jane Adventures
• Star Trek: Deep Space Nine (sometimes abbreviated DS9), is a science fiction television series rooted in Gene Roddenberry’s Star Trek universe
• In Total Drama Action, Trent is obsessed with the number 9.

Other fields

International maritime signal flag for 9

Playing cards showing the 9 of all four suits

• U.S. Route 9, from New York to Delaware.
• In the NATO phonetic alphabet, the digit 9 is called "Novenine".
• Five-digit produce PLU codes that begin with 9 are organic.
• Nine justices sit on the United States Supreme Court.
• The word "K-9" pronounces the same as canine and is used in many U.S. police departments to denote the police dog unit.
• There are nine circles of Hell in Dante's Divine Comedy.
• Stanines, a method of scaling test scores, range from 1 to 9.
• Someone dressed "to the nines" is dressed up as much as they can be.
• The Japanese consider 9 to be unlucky because it sounds similar to the Japanese word for "pain" or "distress" (苦 kunrei ku)^{[citation needed]}.
• The Nine Worthies are nine historical, or semi-legendary figures who, in the Middle Ages, were believed to personify the ideals of chivalry
• The nine bows is a term used in Ancient Egypt to represent the traditional enemies of Egypt
• 9: The Last Resort was a 1995 computer game
• Magic: The Gathering has a set of nine rare cards, widely regarded as overpowered, known as the Power Nine
• Ninth Avenue is a major avenue in Manhattan.
• Nine Unknown Men are, in occult legend, the custodians of the sciences of the world since ancient times
• The 9 on Yahoo!, hosted by Maria Sansone.
• In the game of Craps, 9 is known as the center field because it is in the middle of the seven numbers on the field bet
• In Middle Earth, there are nine rings of power given to men, and consequently, nine ringwraiths
• The Nine Tailors is a 1934 mystery novel by British writer Dorothy L. Sayers, her ninth featuring sleuth Lord Peter Wimsey
• "A cat-o'-nine-tails suggests perfect punishment and atonement." --Robert Ripley.
• The Nine Bright Shiners, characters in Garth Nix's Old Kingdom trilogy. The Nine Bright Shiners was a 1930s book of poems by Anne Ridler^[8] and a 1988 fiction book by Anthea Fraser;^[9] the name derives from "a very curious old semi-pagan, semi-Christian" song.^[10]
• The character Cirno from the Touhou series is often called "nine," "⑨," "circle-nine," or "nineball," because in the game manual for "Phantasmagoria of Flower View," she was labeled (9) Idiot (⑨ バカ, ⑨　baka^?).^[11]
• The nine muses in Greek mythology are Calliope (epic poetry), Clio (history), Erato (erotic poetry), Euterpe (lyric poetry), Melpomene (tragedy), Polyhymnia (song), Terpsichore (dance), Thalia (comedy), and Urania (astronomy).
• Divine Nine—The National Pan-Hellenic Council (NPHC) is a collaborative organization of nine historically African American, international Greek lettered fraternities and sororities.
• In urban culture, 'nine' is a slang word for a 9mm pistol or homicide, the latter from the Illinois Criminal Code for homicide.