In math, we write a set using curly braces containing its elements. For example, a set typically appears in an expression like this:
In plain langauge, this represents the set containing the elements , , and .
An empty set, also called the null set, is respresented as a zero with a diagonal line through it or as an empty pair of curly braces.
A subset is denoted by the symbol ⊂ and is used to indicate that one set is a subset of another set, but not equal to it.
A superset is denoted by the superset symbol ⊃ and is used to indicate that one set is a superset of another set, but not equal to it.
The subset or equal symbol ⊆ is used in math to denote that one set is a subset of another set or is equal to another set.
The superset or equal symbol ⊇ is used in math to denote that one set is a superset of another set or is equal to another set.