https://www.musical-u.com/learn/when-learning-intervals-be-mindful-of-the-gap/
Sometimes, as we become more familiar with music theory, we start taking the fundamentals for granted. After all, a step is a step, right? In order to really develop your ear, though, it can be surprisingly helpful to look at the basic functions of an interval with fresh eyes. https://www.musical-u.com/learn/when-learning-intervals-be-mindful-of-the-gap/