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This world is a planet where a society of people has formed.

Authors sometimes invent new worlds. The authors use these worlds as the setting for their stories. Some authors invent worlds that have magic.

Nobody knows whether there are intelligent beings on other worlds.

World literature is literature that is read by many people all over this world. World literature is different from national literature.

I am more and more convinced that poetry is the universal possession of mankind, revealing itself everywhere and at all times in hundreds and hundreds of men. . . . I therefore like to look about me in foreign nations, and advise everyone to do the same. National literature is now a rather unmeaning term; the epoch of world literature is at hand. – Johann Wolfgang von Goethe, 1827

Creating a different world is a literary device used by authors to illustrate ideas. By placing the story in the setting of a different world, the author can change the way that things happen in the world. For example, the author might imagine a world that has very little water or a world that has very little dry land. Deciding what the world looks like and how the world works is called world-building. Thinking about the world helps the author make good choices about what happens to the characters in the story. Some authors think about many details, such as what languages the characters speak and what the architecture is on the world.

Science fiction stories often use different worlds. Frank Herbert's famous Dune series focused on a world called Arrakis that produces a rare chemical substance.

Often a science-fiction story will be involve multiple worlds. The Foundation series by Isaac Asimov was set in a galaxy with thousands of populated worlds. The Star Wars movies had a several important worlds, and characters traveled between them. Some authors of science fiction worlds try to make them scrupulously obey the laws of physics.

Fantasy worlds are fictional worlds that use magic. This magic may involve saying magic words, using magical objects, or performing magical rituals.

Some languages spoken in many parts of the world. These are called world languages. As of 2016, English is the most common world language. Previously, French was the most popular language in the West. Chinese was used by traders in all of East Asia for centuries. Arabic is common in the Middle East, Northern Africa, and other parts of the world.

Once upon a time, Greek and Latin were spoken by most traders in the Western world. Before then, traders learned the languages of nearby cities. Ancient traders did not travel around the world.

The Egyptians used pictures to write their language. The pictures are called hieroglyphics. This is what they look like:

The World Health Organisation (French: Organisation mondiale de la santé) is an international organisation for public health.^[1] It is part of the United Nations. The World Health Organisation began in 1948.^[1] It wants people to be healthy and safe. It studies public health and tells governments and other organisations how to help people become healthy.

The organisation counts the number of people with health problems. These health problems include influenza, HIV infection, and depression. It also counts the number of people who experience other problems. These problems include dirty water, violence, and hunger.

Mental health is also important.^[2] People with mental health problems such as depression often die ten years early.

The World Bank is also interested in health.^[3] Health affects economic prospects.

This poem by John Donne mentions the world:

The entire poem can be read at Wikisource.

This world is not a perfect sphere. It is slightly flattened. This is the mathematical formula for measuring the flatness of a sphere:

${\displaystyle \begin{array}{ll}f& =\frac{a-b}{a}.\end{array}}$

For this world, $f$ is approximately 0.3%. The Moon is rounder. For the Moon, $f$ is approximately 0.1%. Jupiter is flatter. For Jupiter, $f$ is approximately 6.5%.

A world is on a planet. There are different types of planets. There are several types of planets in this solar system:

• Terrestrial planets
• Giant planets
  • Gas giants
  • Ice giants

These are the planets in this solar system:

• Four terrestrial planets
  1. Mercury
  2. Venus
  3. Earth
     • One satellite, called the Moon
  4. Mars
• Two gas giants
  1. Jupiter
     • Four large satellites
     • 63 other satellites
  2. Saturn
     • 62 satellites. Some are very small. The largest, called Titan, is larger than the planet Mercury.
     • Seven are large.
• Two ice giants
  1. Uranus
     • Five satellites
     • 22 other satellites
  2. Neptune
     • One satellite, called Triton

• Comparison of local planets (not to scale)
• 
  Mercury
• 
  Venus
• 
  Earth
• 
  Mars
• 
  Jupiter
• 
  Saturn
• 
  Uranus
• 
  Neptune

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• [1] – an external link without a label