The purpose of expository presentation is to

The purpose of an expository presentation is to explain, clarify, or define an idea, theory, or process.

The structure of this type of presentation consists of two elements: The points to explain as the main topic, and the points to sustantiate one's claims on the main point.

postive, comparative, superlative - good, better, best

recall how we defined nouns as words capable of having plurals and possessive endings. adjectives (and their first cousin, the adverb) also have a feature that distinguishes them. they come in three states. first, the raw adjective—in its positive state—merely describes the noun modified; it doesn’t care about how this particular person or thing stacks up against other members of the same noun class