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ELI5 Yahaaa

A number for nothing

What Is Zero?

Zero counts what is not there — and that turned out to be one of our best ideas.

Three apples You can point at themZero apples0You can still countthem
Naming nothing is harder than it sounds.

  1. Step 1 of 5

    Counting starts with things you can see.

    OneTwoThree

    One sheep, two sheep, three sheep. Every early counting system began this way — a number always stood for something in front of you.

  2. Step 2 of 5

    But an empty pen still needs a number.

    A gap on the tablet Is it nothing, or asmudge?A written 00Unmistakably none

    If all the sheep are gone you have a real, useful fact to record. For thousands of years people had no symbol for it and simply left a gap.

  3. Step 3 of 5

    Zero also holds a place.

    Written 252Two tens and fiveWritten 205 Two hundreds, no tens,five

    In 205, the zero is not counting nothing — it is saying there are no tens. Without it, 205 and 25 would look identical.

  4. Step 4 of 5

    It makes arithmetic behave.

    1 Count up fromzero20Zero sits inthe middle3−Count down pastit intonegatives

    Add zero to anything and it stays the same. Subtract a number from itself and you land on zero. It is the resting point of the whole number line.

  5. Step 5 of 5

    Multiplying by zero wipes everything out.

    5 × 3 Fifteen5 × 00Nothing — every time

    Seven groups of nothing is nothing. A million groups of nothing is still nothing. Zero is the only number that does this.

    Zero reached Europe from India via Arab mathematicians around 1200. Some cities banned it as suspicious.

The short version

Zero counts nothing and holds empty places — and without it, our number system would not work.

Try it yourself

Write 507 and then take away the zero. The number instantly becomes a different, much smaller thing.

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