subset

In mathematics and logic, a set is a collection of distinct objects, called elements. These elements can be anything, such as numbers, functions, or even other sets. Sets are typically represented by enclosing their elements in braces, like {1, 2, 3}.

A set can be finite, like the numbers from 1 to 100, or infinite, like all integers. To indicate an object is part of a set, we use the symbol ∈ (e.g., x ∈ A). If an object is not in a set, we use ∉ (e.g., x ∉ A). An empty set, with no members, is denoted by Ø.1

A subset (symbolized by ⊆) is a set where all of its elements are also found in another, larger set. For example, {1, 2} is a subset of {1, 2, 3}. Any set is a subset of itself, and the empty set is a subset of every set.1

Sets can be combined using operations like union (∪), which creates a new set containing all elements from both sets, and intersection (∩), which creates a new set containing only elements common to both sets.1