Ordered Pair

Let $x$ and $y$ be objects. Write $\{x\}$ for the set whose only element is $x$, and $\{x,y\}$ for the set whose elements are exactly $x$ and $y$.

The \textbf{ordered pair} of $x$ and $y$ is the set

In this expression $x$ is the \textbf{first component} and $y$ is the \textbf{second component}.