Editing Introduction to Set theory (section)

== What is a Set? ==

A '''set''' is a collection of objects, called '''elements''' or '''members''', that are grouped together because they share a common property.

* Example: A set of vowels in the English alphabet is written as:
<math>A = \{a, e, i, o, u\}</math>

=== Notation and Terminology ===

* Sets are usually denoted by '''capital letters''' like A, B, C.
* Elements are written '''within curly brackets''' <math>\{\}</math>.
* The symbol '''∈''' means “is an element of”.
  * Example: <math>3 \in \{1, 2, 3\}</math>
* The symbol '''∉''' means “is not an element of”.
  * Example: <math>4 \notin \{1, 2, 3\}</math>