Set Notation

You write sets with curly braces. For example, $A = \{1, 2, 3\}$ means set $A$ contains the numbers $1$, $2$, and $3$.

You can make sets from anything: numbers, letters, words, or even other sets. For example, $B = \{\text{apple}, \text{banana}, \text{cherry}\}$ is a set of fruits.

Order does not matter, so $\{1, 2\}$ is the same as $\{2, 1\}$. Duplicates disappear automatically: $\{1, 1, 2\} = \{1, 2\}$.