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# Sets and elements

A set is a collection of elements. It is described by all its elements.

The set $\N$ of the natural numbers consists of 1, 2, etc.

The set of the letters of ALI BABA consists of the elements A, L, I and B.

When we define the set by listing its elements, we put them in braces (curly brackets { }) separated by commas.

The set of the letters of ALI BABA is written as $\{A,B,I,L\}$.

The set of the integers can be written as $$\Z =\{0, 1, -1, 2, -2, 3, -3, \dots\}$$

The order in which the elements are written does not matter.

$\{0,1,3,5\}$ and $\{3,1,5,0\}$ are the same set.

The set of the primary and secondary colours.