Gray defines psoriasis in this example of autobiographical writing.
Defining is an essential strategy for all writing. Autobiographers, for example, must occasionally define objects, conditions, events, and activities for readers likely to be unfamiliar with particular terms, as in the following example:
My father’s hands are grotesque. He suffers from psoriasis, a chronic skin disease that covers his massive, thick hands with scaly, reddish patches that periodically flake off, sending tiny pieces of dead skin sailing to the ground.
—JAN GRAY, “Father”
Olson defines shifting baselines in this example of explanatory writing.
When writers share information or explain how to do something, they must often define important terms for readers who are unfamiliar with the subject, as in this example:
Shifting baselines are the chronic, slow, hard-to-notice changes in things, from the disappearance of birds and frogs in the countryside to the increased drive time from L.A. to San Diego.
—RANDY OLSON, “Shifting Baselines: Slow-Motion Disaster below the Waves”
Ehrenreich defines extreme poverty in this example of argument.
To convince readers of a position or an evaluation or to move them to act on a proposal, a writer must often define concepts important to an argument:
You would come across news of a study showing that the percentage of Wisconsin food-stamp families in “extreme poverty”—defined as less than 50 percent of the federal poverty line—has tripled in the last decade to more than 30 percent.
—BARBARA EHRENREICH, Nickel and Dimed
As these examples illustrate, there are many kinds of definitions and many forms that they can take. Some published essays and reports are primarily concerned with the definition of a little-understood or problematic concept or thing. Usually, however, definition is only a part of an essay. A long piece of writing, like a term paper, textbook, or research report, may include many kinds of brief and extended definitions, all of them integrated with other writing strategies.
This chapter illustrates various types of sentence definitions, the most common in writing. When writers use sentence definitions, they rely on various sentence patterns to provide concise definitions. The chapter also provides illustrations of multi-sentence extended definitions, including definition by word history, or etymology, and by stipulation. It concludes with some sentence strategies you might use to get started drafting a definition.