Collection of distinct objects that have a common characteristic (

*defining property*) called elements in this set.A set is extensionally defined when it is defined by the explicit list of its elements, such as: U = {6, 7, 8, 9, 10, 11, 12} or \(\mathbb{N}\) = {0, 1, 2, 3, 4, 5, 6, 7, …}.

A set is intensionally defined when it is defined by one of its characteristic properties, such as: H = {*x* ∈ \(\mathbb{N}\) | *x* > 5 and *x* < 13}.

### See also :

- Set of destination (or image set) of a relation
- Countable set
- Set of departure of a relation
- Set of numbers
- Set that is closed under an operation
- Finite set
- Infinite set
- Ordered set
- Solution set
- Universal set
- Empty set