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Number

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Numbers are special objects used to count, measure, and label the world.

Ishango bone (cropped)
Ishango bone (cropped)

We use them to see how many things are in a group. We also use them as labels, like for a phone numbers. Numbers can also be used for ordering, such as with serial numbers. There is a difference between a number and a numeral. A number is the idea of the amount itself. A numeral is the symbol we write down to show that number.

For example, "eleven" is a number word. The symbol "11" is a numeral. We use numeral systems to keep things organized. The most common one is the Hindu-Arabic system. This system uses ten digits to show any non-negative integer.

Math uses many different kinds of numbers to solve problems. Natural numbers are the simplest, like 1, 2, and 3. Rational numbers are like fractions, which show parts of a whole.

Venn Diagram of Numbers Expanded
Venn Diagram of Numbers Expanded

We also use negative numbers to show things like debt. Real numbers include things like pi or the square root of 2.

Archimedes pi
Archimedes pi

Some even more advanced ideas are called complex numbers. We use arithmetic to work with these numbers. This includes adding, subtracting, multiplying, and dividing. People also use exponentiation to grow numbers quickly. Studying these properties is called number theory.

People have been using numbers for a very long time.

YBC-7289-OBV-labeled
YBC-7289-OBV-labeled

Some very old bones have marks cut into them. The Lebombo bone is about 43,000 years old. The Ishango bone is between 22,000 and 30,000 years old. Historians think these might be tally marks for counting. They might have tracked days or the number of animals. These early systems did not have place value. This made it hard to show very large numbers. Later, the Mesopotamians used a base 60 system around 3400 BC. The Egyptians used a base 10 system by 3100 BC.

One of the most important ideas is the number zero.

Khmer Numerals - 605 from the Sambor inscriptions
Khmer Numerals - 605 from the Sambor inscriptions

For a long time, people used zero just as a placeholder. The Indian mathematician Brahmagupta was a pioneer here. In his work from AD 628, he treated zero as a real number. He wrote rules for adding and subtracting zero. He even discussed dividing by zero. The concept spread to China and the Islamic world. It reached Europe around the year 1000. The Maya people also used a placeholder symbol for zero. They used a shell glyph by 38 BC.

Numbers help us understand how the universe works.

Maya
Maya

We can use them to find the area of a circle. The Babylonians even had an estimate for pi long ago. Their clay tablets showed a value of 3.125. This was a very early approximation of pi. We see numbers in patterns and in the shapes of objects. They help us build things and keep records. From counting snacks to launching rockets, numbers are everywhere. They turn the world into something we can measure and understand.

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🖼️ Images & Media (15)
File:Venn Diagram of Numbers Expanded.svg
Venn Diagram of Numbers Expanded.svg
File:Archimedes pi.svg
Archimedes pi.svg
File:SimilarGoldenRectangles.svg
SimilarGoldenRectangles.svg
File:Largest known prime number.svg
Largest known prime number.svg
File:NumberSetinR2.svg
NumberSetinR2.svg
File:Numeral Systems of the World.svg
Numeral Systems of the World.svg
File:Maya.svg
Maya.svg
File:Euler's formula caimi.svg
Euler's formula caimi.svg
File:Nat num.svg
Nat num.svg
File:The Ancient Quipu Plate XXI.jpg
The Ancient Quipu Plate XXI.jpg
File:Mandel zoom 00 mandelbrot set.jpg
Mandel zoom 00 mandelbrot set.jpg
File:YBC-7289-OBV-labeled.jpg
YBC-7289-OBV-labeled.jpg

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