Is P a subset. However it is not universally used and so you should make sure to define it whenever you use it. Defining sets by properties is also known as set comprehension set abstraction or as defining a sets intension.
Let P be the set of all people who have at least one pet.
If the order of the elements is changed or any element of a set is repeated it does not make any changes in the set. Defining sets by properties is also known as set comprehension set abstraction or as defining a sets intension. The things in the set are called the elements and are listed inside curly braces. Sets in mathematics are an organized collection of objects and can be represented in set-builder form or roster form.