Question

The key words in a sentence often include

Answer 1

Keywords are the words that academics use to reveal the internal structure of an author's reasoning. While they are used primarily for rhetoric, they are also used in a strictly grammatical sense for structural composition, reasoning, and comprehension. Indeed, they are an essential part of any language.

There are many different types of keyword categories including: Conclusion, Continuation, Contrast, Emphasis, Evidence, Illustration and Sequence. Each category serves its own function, as do the keywords inside of a given category.
Source http://en.wikipedia.org/wiki/Keywords