There are basically two steps that go in a cycle. Old words from the English language are taken, and they are changed in how they sound and what they mean, making a slang, sometimes slowly sometimes quickly the slang terms become excepted as words by society and eventually they become the words being changed. If you think about it the language changes based on what we find to be the way the popular people talk. In the past it was the rich or the actors/esses in plays that started a change in culture, now it are the musicians and actors/esses. That is what I think about it, there are probably more ways of explaining it, if I even answered that the way you wanted.
I think the morbidity rate is the frequency or proportion with which a disease appears in a population. The trend in the morbidity rate is that it fluctuated over the last ten years with a significant spike in 2010 and a rapidly increasing trend from 2014-2016 until a sudden decline in 2017.
