👉 Semilong is a term used in mathematics to refer to a type of infinite series that diverges. In this context, "semilong" refers to an infinite series that has both positive and negative terms. For example, consider the series: $$\sum_{n=1}^{\infty}\frac{(-1)^n}{n!}.$$ This series diverges because it is not convergent at all, meaning that its limit does not exist.