8 (eight) is the natural number following 7 and preceding 9.

The SI prefix for 1000⁸ is yotta (Y), and for its reciprocal yocto (y).

Evolution of the glyph

In the beginning, various groups in India wrote 8 more or less in one stroke as a curve that looks like an uppercase H with the bottom half of the left line and the upper half of the right line removed. At one point this glyph came close to looking like our modern 5. With the western Ghubar Arabs, the similarity of the glyph to 5 was banished by connecting the beginning and the end of stroke together, and it was only a matter of the Europeans rounding the glyph that led to our modern 8.

In mathematics

It is a composite number, its proper divisors being 1, 2, and 4. Eight is a power of two, being 2³, or two cubed.

8 is the base of the octal number system, which is mostly used with computers. In octal, one digit represents three bits.

The number 8 is a Fibonacci number, being 3 plus 5. The next Fibonacci number is 13.

In binary code eight is 1000; in ternary code eight is 22; in quaternary numeral system code eight is 20; in quinary eight is 13; in senary eight is 12; in septenary eight is 11; in octal eight is 10; in novenary code and all codes above (such as decimal and hexadecimal) eight is 8. In Roman numerals eight is VIII.

A polygon with eight sides is an octagon. Figurate numbers representing octagons (including eight) are called octagonal numbers. A polyhedron with eight faces is an octahedron.

Sphenic numbers always have exactly eight divisors.

In science

• The atomic number of oxygen
• The second Magic number (physics).
• In particle physics, the eightfold way is used to classify sub-atomic particles.

In astronomy,

Messier object M8, a magnitude 5.0 nebula in the constellation Sagittarius.

The New General Catalogue object NGC 8 , a double star in the constellation Pegasus

The Saros number of the solar eclipse series which began on -2579 March 7 and ended on -1281 April 26. The duration of Saros series 8 was 1298.1 years, and it contained 73 solar eclipses.

The Saros number of the lunar eclipse series which began on -2512 July 27 and ended on -961 February 13. The duration of Saros series 7 was 1550.6 years, and it contained 87 lunar eclipses.

In other fields

• Eight (八, formal writing 捌, pinyin bā) is considered a lucky number in Chinese culture because it sounds like the word "prosper" (發 pinyin fā).
• There are eight musicians in an octet.
• Eight babies delivered in one birth are called octuplets. The first set of eight surviving babies, the Louis-Chukwu Octuplets, were born in 1998.
• All spiders, and more generally all arachnids, have eight legs. An octopus has eight tentacles.
• Timothy Leary identified a hierarchy of eight levels of consciousness.
• The wheel of life has eight spokes.
• October was the eighth month in the Roman calendar, August is currently the eighth month.
• The Noble Eightfold Path in the Buddhist faith has eight steps.
• Eight is not safe to be said by wizards on the Discworld and is the number of Bel-Shamharoth. Also, there are eight days in a Disc week and eight colours in a Disc spectrum, the eighth one being octarine.
• Referring to the shape of the numeral, eight was represented in bingo slang, before political correctness, as 'One Fat Lady.' Eighty-eight was 'Two Fat Ladies'.
• Eight ball billiards is played with 15 balls; the black ball numbered 8 is the most important one. Magic 8 Ball is a randomized process of predicting the future or answering various questions, packaged to resemble this ball and often sold as a fortune-telling device.
• "Eight maids a-milking" is the gift on the eighth day of Christmas in the "Twelve days of Christmas" carol.
• I-8 is the designation of the US interstate highway that runs from San Diego, California to Casa Grande, Arizona.
• Eight is the number of categories the VALS system uses to classify consumer groups, and the number of categories used by Fallon-McElligott 's system for teen marketing.
• There is a brand of chocolate called "After Eight", referring to the time 8 p.m.
• There are eight vegetables in V8 juice.
• The number on Walt Disney's Herbie adds up to eight.
• In Astrology, Scorpio is the 8th astrological sign of the Zodiac.
• Using hyperbole, the Beatles sang about loving their addressee "Eight Days a Week". Also from music is the 8-track.
• A note played for one-eighth the duration of a whole note is called an eight note, or quaver.
• The numeral "8" is sometimes used in writing to represent the syllable "ate", as in writing "H8" for "hate", or "congratul8ons" for "congratulations". Avril Lavigne's song "Sk8er Boi" uses this convention in the title.
• Several groups of "Eight Immortals"
• Eight Principles of Yong
• War of the Eight Princes
• In chess, each side has eight pawns; see also Eight queens puzzle
• In rugby union the number eight central back row position wears the 8 shirt.
• In baseball, eight represents the center fielder's position.
• The silver piece of eight was coined in the Spanish Empire and moved trade around the world.
• The symbol for infinity looks like a fallen eight.
• A figure 8 is the common name of a geometric shape, often used in the context of sports, such as skating.
• Lewis Carrolls poem The Hunting of the Snark has 8 "fits" (cantos), which is noted in the full name "The Hunting of the Snark - An Agony, in Eight Fits.
• In Terry Pratchett's Discworld series, eight is a holy number and is considered taboo.
• "Section 8" is common U.S. slang for "crazy", based on the U.S. military's Section 8 discharge for mentally unfit personnel.
• Historical years: 8 A.D., 8 B.C., or 1908
• The Nintendo Entertainment System has eight bits