“Prototypes,” she muttered. “What does that even mean?”

In the vast ocean of written communication—from viral tweets to legal contracts, from fairy tales to scientific reports—how do we distinguish one form of writing from another? What makes a story a story? What makes an argument an argument?

This is the sequence of command, instruction, or advice. It ranges from recipes to legal laws. Its typical markers are the imperative mood, the infinitive, or the future tense of command ("You will do...").

Adam’s genius was recognizing that texts are heterogeneous . His 1992 book, often sought as the , proposes a solution: the sequence .