Number
Numbers are not apparent in nature as physical entities.
Explanation
A number can contain digits, letters and symbols. They are often used to indicate a position within a hierarchy, as for house numbering. But sometimes there is not even an hierarchy as with telephone numbers.
Representations
Sometimes, numbers are represented as beads on a string. Each bead has a number, and so you get a kind of number line. It looks like a rosary. That image can be used for simple calculations. It can also lead to confusion.
The addition 1/2 + 1/2 = 1 cannot be explained by this, allthough a child will understand it. Maybe there are large and small beads?
Use images and pictures only if they help. But always keep in mind that applies: a number is a number. That is all.
Example 1
Numbers are no points. You can write the number 1 as 0.999... and then you don't know if this is the same point. If you delete the point 1 will the point 0.999... then remain or does it disappear aswell?
Example 2
You can indicate numbers with letters. You call this the number x, a, e, i or π, etc. It often involves constants, variables, or parameters.
Example 3
A number can be written as
12 2,5 8 1/2 0,9999... 6a2 √2
A house number can be written as
12A
A telephone number can consist of
A flight number can be
B 3752 HL