# What are Venn diagrams?

A Venn diagram is a way of grouping different items. These groups are known as sets.

We have a set of golf clubs or a set of dishes – these are just groups of those items.

We write a set using a special type of brackets. You could have a set of friends, eg {tom, leanne, alison, nia, anna, suzanne, lucy, marie}. Notice you don’t use capitals within the brackets.

A Venn diagram begins with a box called our universal set, which is denoted by the symbol $$ε$$ (epsilon).

The universal set contains everything we are interested in at that particular time. There’ll be circles inside the box which we use to group the items within the universal set. Items in the circles form different subsets.

### Subsets

Set A is the numbers in the circle labelled Set A.

Set A = {1, 5, 6, 7, 8, 9, 10, 12}

Set B is the numbers in the circle labelled Set B.

Set B = {2, 3, 4, 6, 7, 9, 11, 12, 13}

These are the subsets of the universal.

### Intersection

The intersection is where we have items from Set A and Set B, these can be found in the section that overlaps.

We write it as $${A}\cap{B}$$. In the example above $${A}\cap{B}$$ = {6, 7, 9, 12}.

### Union

The union of a Venn diagram is the numbers that are in either Set A or Set B.

The union of the above example is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13 as it’s the numbers that appear in either of the circles.

We write it as $${A}\cup{B}$$ = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13}