A sequence or list $a_i$ is said to be strictly monotonically increasing if for each pair of adjacent elements the successor is greater than its predecessor, or: $a_i < a_{i+1}$.
But what if there is no such pair, because the list contains only 1 or 0 elements?
Is such a sequence strictly monotonic, because there is no pair that violates the condition? Or is it not strictly monotonic, because there is no pair that satisfies the condition? Or is it undefined?
A sequence of only one (or no) element is both strictly increasing and strictly decreasing due to the logical phenomenon known as "vacuous truth".
Basically, it means that the condition is true because there are no counterexamples.