Extended real number line

In mathematics, the extended real number system is obtained from the real number system R {\displaystyle \mathbb {R} } by adding two elements denoted + ∞ {\displaystyle +\infty } and − ∞ {\displaystyle -\infty } that are respectively greater and lower than every real number. This allows for treating the potential infinities of infinitely increasing sequences and infinitely decreasing series as actual infinities.

Source: Wikipedia — Extended real number line (CC BY-SA 4.0)