A **finite** set is a set whose members are *countable*. Examples of finite sets are:

**1**. K = {1, 3, 5, 7, 11}

**2**. C = {Students in Aboodo High School}

An **infinite** set is a set whose members are *uncountable*. Examples of infinite sets are:

**1**. A = {1, 2, 3, 4 …}

**2**. B = {Even numbers}

Suppose

A = {1, 3, 5, 7, 9, 11} and

B = {1, 5, 9}

We may say that B is a **subset** of A since all the members of set B are also members of set A. In symbols, we would express the relationship like this: **B⊂A** (read *B is a subset of A*) or **A⊃B** (read *A is a superset of B*).

To find all the subsets of a set, note that *the empty or null set,* { } or Ø,

*is a subset of any set*.

Also note that *any set is a subset of itself*.

**Question**: Find all the subsets of set Y = {3, 5, 7}.

**Answer**:

The subsets of set Y = {3, 5, 7} are:

Ø, {3}, {5}, {7}, {3, 5}, {3, 7}, {5, 7}, {3, 5, 7}

When discussing sets, it’s useful to assume that all the sets under consideration are subsets of a well-defined set – **the universal set**.