The starting point.

On a number line it is 0

On a two-dimensional graph it is where the X axis and Y axis cross, such as on the graph here:

Sometimes written as the letter

In three dimensions it is the point (0, 0, 0) where the x, y and z axis cross:

On a number line it is 0

On a two-dimensional graph it is where the X axis and Y axis cross, such as on the graph here:

Sometimes written as the letter

**O**In three dimensions it is the point (0, 0, 0) where the x, y and z axis cross:

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