Teaching Material Class 7, Class 8, Class 9, Class 10 Maths Sets - Notes

Definition
What is a set? Well, simply put, it's a collection.
First we specify a common property among "things" (we define this word later) and then we gather
up all the "things" that have this common property.

For example, the items you wear: shoes, socks, hat, shirt, pants, and so on.
I'm sure you could come up with at least a hundred.
This is known as a set.

Or another example is types of fingers.

This set includes index, middle, ring, and pinky.

So it is just things grouped together with a certain property in common.

Notation
There is a fairly simple notation for sets. We simply list each element (or "member") separated by a
comma, and then put some curly brackets around the whole thing:

{ 3, 6, 91, ... }
element three dots means
element goes on forever (infinite)
element
("element" or "member" mean the same thing)

The curly brackets { } are sometimes called "set brackets" or "braces".
This is the notation for the two previous examples:
{socks, shoes, watches, shirts, ...}
{index, middle, ring, pinky}
Notice how the first example has the "..." (three dots together).
The three dots ... are called an ellipsis, and mean "continue on".
So that means the first example continues on ... for infinity.