set

A set is a collection of distinct objects (i.e. members, elements). By this definition, sets cannot contain duplicate elements.

Here are some commonly used sets:

• $\mathbb{Z}$: integers
• $\mathbb{N}$: natural numbers, i.e. nonnegative integers
• $\mathbb{R}$: real numbers
• $\mathbb{Q}$ rational numbers
• $\varnothing$: empty set