Ordered Pair

An ordered pair is a pair of objects written in a fixed order — usually as $(a, b)$ — where $a$ is called the first component and $b$ the second. The key idea is that $(a, b)$ and $(b, a)$ are different unless $a = b$, because the position matters. This simple notion of "order" is what lets us pin down exactly which two things are related and in which dire …