14: Writing Definitions, Descriptions, and Instructions

Writing Descriptions

Technical communication often requires descriptions: verbal and visual representations of the physical or operational features of objects, mechanisms, and processes.

Objects. An object is anything from a natural physical site, such as a volcano, to a synthetic artifact, such as a battery. A tomato plant is an object, as is an automobile tire or a book.
Mechanisms. A mechanism is a synthetic object consisting of a number of identifiable parts that work together. A cell phone is a mechanism, as is a voltmeter, a lawnmower, or a submarine.
Processes. A process is an activity that takes place over time. Species evolve; steel is made; plants perform photosynthesis. Descriptions of processes, which explain how something happens, differ from instructions, which explain how to do something. Readers of a process description want to understand the process; readers of instructions want a step-by-step guide to help them perform the process.

Descriptions of objects, mechanisms, and processes appear in virtually every kind of technical communication. For example, an employee who wants to persuade management to buy some equipment includes a description of the equipment in the proposal to buy it. A company manufacturing a consumer product provides a description and a photograph of the product on its website to attract buyers. A developer who wants to build a housing project includes in his proposal to municipal authorities descriptions of the geographical area and of the process he will use in developing that area. A maintenance manual for an air-conditioning system might begin with a description of the system to help the reader understand first how it operates and then how to fix or maintain it.

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ANALYZING THE WRITING SITUATION FOR DESCRIPTIONS

Before you begin to write a description, consider carefully how the audience and the purpose of the document will affect what you write.

Your sense of your audience will determine not only how technical your vocabulary should be but also how long your sentences and paragraphs should be. Another audience-related factor is your use of graphics. Less-knowledgeable readers need simple graphics; they might have trouble understanding sophisticated schematics or decision charts. As you consider your audience, think about whether any of your readers are from other cultures and might therefore expect different topics, organization, or writing style in the description.

Consider, too, your purpose. What are you trying to accomplish with this description? If you want your readers to understand how a personal computer works, write a general description that applies to several brands and sizes of computers. If you want your readers to understand how a specific computer works, write a particular description. Your purpose will determine every aspect of the description, including its length, the amount of detail, and the number and type of graphics.

DRAFTING EFFECTIVE DESCRIPTIONS

There is no single organization or format used for descriptions. Because descriptions are written for different audiences and different purposes, they can take many shapes and forms. However, the following four suggestions will guide you in most situations:

Indicate clearly the nature and scope of the description.
Introduce the description clearly.
Provide appropriate detail.
End the description with a brief conclusion.

For more about titles and headings, see “Writing Clear, Informative Titles and Headings” in Ch. 6.

Indicate Clearly the Nature and Scope of the Description If the description is to be a separate document, give it a title. If the description is to be part of a longer document, give it a section heading. In either case, clearly state the subject and indicate whether the description is general or particular. For instance, a general description of an object might be entitled “Description of a Minivan,” and a particular description, “Description of the 2015 Honda Odyssey.” A general description of a process might be called “Description of the Process of Designing a New Production Car,” and a particular description, “Description of the Process of Designing the Chevrolet Malibu.”

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Introduce the Description Clearly Start with a general overview: you want to give readers a broad understanding of the object, mechanism, or process. Consider adding a graphic that introduces the overall concept. For example, in describing a process, you might include a flowchart summarizing the steps in the body of the description; in describing an object, such as a bicycle, you might include a photograph or a drawing showing the major components you will describe in detail in the body.

Table 14.1 shows some of the basic kinds of questions you might want to answer in introducing object, mechanism, and process descriptions. Figure 14.2 below shows the introductory graphic accompanying a description of an electric bicycle.

Figure 14.2: Figure 14.2 Graphic with Linked Graphics and Descriptions

Source: Trek Bicycle Corporation, 2013: http://www.trekbikes.com/us/en/collections/electric_assist/feature_tour.

Clicking on any of the red dots opens a window with a one-sentence description and graphic, as well as a link to an extended description and more-detailed graphic.

This web-based description includes six labeled systems. Here we see the expanded description of one of them: the regenerative braking system.

TABLE 14.1 Transitional Words and Phrases
FOR OBJECT AND MECHANISM DESCRIPTIONS	FOR PROCESS DESCRIPTIONS
What is the item? You might start with a sentence definition. What is the function of the item? If the function is not implicit in the sentence definition, state it: “Electron microscopes magnify objects that are smaller than the wavelengths of visible light.” What does the item look like? Sometimes an object is best pictured with both graphics and words. Include a photograph or drawing if possible. (See Chapter 8 for more about incorporating graphics into your text.) If you cannot use a graphic, use an analogy or comparison: “The USB drive is a plastic- or metal-covered device, about the size of a pack of gum, with a removable cap that covers the type-A USB connection.” Mention the material, texture, color, and other physical characteristics, if relevant. Where and when does the process take place? “Each year the stream is stocked with hatchery fish in the first week of March.” Omit these facts only if your readers already know them. How does the item work? In a few sentences, define the operating principle. Sometimes objects do not “work”; they merely exist. For instance, a ship model has no operating principle. What are the principal parts of the item? Limit your description to the principal parts. A description of a bicycle, for instance, would not mention the dozens of nuts and bolts that hold the mechanism together; it would focus on the chain, gears, pedals, wheels, and frame.	What is the process? You might start with a sentence definition. What is the function of the process? Unless the function is obvious, state it: “The main purpose of performing a census is to obtain current population figures, which government agencies use to revise legislative districts and determine revenue sharing.” Who or what performs the process? If there is any doubt about who or what performs the process, state that information. How does the process work? “The four-treatment lawn-spray plan is based on the theory that the most effective way to promote a healthy lawn is to apply different treatments at crucial times during the growing season. The first two treatments—in spring and early summer—consist of . . . .” What are the principal steps in the process? Name the steps in the order in which you will describe them. The principal steps in changing an automobile tire, for instance, are jacking up the car, replacing the old tire with the new one, and lowering the car back to the ground. Changing a tire also includes secondary steps, such as placing chocks against the tires to prevent the car from moving once it is jacked up. Explain or refer to these secondary steps at the appropriate points in the description.

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Provide Appropriate Detail In the body of a description—the part-by-part or step-by-step section—treat each major part or step as a separate item. In describing an object or a mechanism, define each part and then, if applicable, describe its function, operating principle, and appearance. In discussing the appearance, include shape, dimensions, material, and physical details such as texture and color (if essential). In describing a process, treat each major step as if it were a separate process.

A description can have not only parts or steps but also subparts or substeps. A description of a computer system includes a keyboard as one of its main parts, and the description of the keyboard includes the numeric keypad as one of its subparts. And the description of the numeric keypad includes the arrow keys as one of its subparts. The same principle applies in describing processes: if a step has substeps, you need to describe who or what performs each substep.

Conclude the Description A typical description has a brief conclusion that summarizes it and prevents readers from overemphasizing the part or step discussed last.

A common technique for concluding descriptions of mechanisms and of some objects is to state briefly how the parts function together. A process description usually has a brief conclusion: a short paragraph summarizing the principal steps or discussing the importance or implications of the process.

A LOOK AT SEVERAL SAMPLE DESCRIPTIONS

A look at some sample descriptions will give you an idea of how different writers adapt basic approaches for a particular audience and purpose.

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Providing Appropriate Detail in Descriptions

Use the following techniques to flesh out your descriptions.

FOR MECHANISM AND OBJECT DESCRIPTIONS

Choose an appropriate organizational principle. Descriptions can be organized in various ways. Two organizational principles are common:
- Functional: how the item works or is used. In a radio, the sound begins at the receiver, travels into the amplifier, and then flows out through the speakers.
- Spatial: based on the physical structure of the item (from top to bottom, east to west, outside to inside, and so forth).
The description of a house, for instance, could be organized functionally (covering the different electrical and mechanical systems) or spatially (top to bottom, inside to outside, east to west, and so on). A complex description can use different patterns at different levels.
Use graphics. Present a graphic for each major part. Use photographs to show external surfaces, drawings to emphasize particular items on the surface, and cutaways and exploded diagrams to show details beneath the surface. Other kinds of graphics, such as graphs and charts, are often useful supplements (see Chapter 8).

FOR PROCESS DESCRIPTIONS
Structure the step-by-step description chronologically. If the process is a closed system—such as the cycle of evaporation and condensation—and therefore has no first step, begin with any principal step.
Explain causal relationships among steps. Don’t present the steps as if they had nothing to do with one another. In many cases, one step causes another. In the operation of a four-stroke gasoline engine, for instance, each step creates the conditions for the next step.
Use the present tense. Discuss steps in the present tense unless you are writing about a process that occurred in the historical past. For example, use the past tense in describing how the Snake River aquifer was formed: “The molten material condensed . . . .” However, use the present tense in describing how steel is made: “The molten material is then poured into . . . .” The present tense helps readers understand that, in general, steel is made this way.
Use graphics. Whenever possible, use graphics to clarify each point. Consider flowcharts or other kinds of graphics, such as photographs, drawings, and graphs. For example, in a description of how a four-stroke gasoline engine operates, use diagrams to illustrate the position of the valves and the activity occurring during each step.

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Figure 14.3 below shows the extent to which a process description can be based on a graphic. The topic is a household solar array. The audience is the general reader.

Figure 14.3: Figure 14.3 A Process Description Based on a Graphic

Source: Vanguard Energy Partners LLC, 2014: http://www.vanguardenergypartners.com/howsolarworks.html.

This description begins with an informal definition of “direct gridtie system.”

In the next section, the writer presents the steps of the process in chronological order.

The description uses boldfaced text to emphasize key terms, most of which appear in the graphic.

The description focuses on the operating principle of the system. It does not seek to explain the details of how the system works. Accordingly, the graphic focuses on the logic of the process, not on the particulars of what the components look like or where they are located in the house.

Figure 14.4 shows an excerpt from a mechanism description of three different types of hybrid drivetrains used in automobiles: series, parallel, and series/parallel.

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This excerpt from a mechanism description begins with an advance organizer that helps the reader make the transition from the previous section (a basic description of hybrid technology) to the present section, which discusses the three types of drivetrains.

The interactive graphic enables the reader to view the principle of operation of three types of hybrid drivetrains, each during five modes. Here, the graphic shows how the components of the series drivetrain work together as the car operates at slow speeds. On the UCS website, the red and green striped lines are animated to highlight the components operating during the mode the reader has selected.

For each of the three types of drivetrains, the text begins with a description of the operating principle, followed by explanations of the strengths and weaknesses of the drivetrain. Notice that the audience and purpose of this description determine the kind of information it contains. Because this description seeks to explain the operating principle behind each of the three types of drivetrains, it focuses on the drivetrains’ functions, not on the materials they are made of or on their technical specifications.

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Figure 14.5: Figure 14.4 Excerpt from a Mechanism Description

Source: Hybrids Under the Hood (Part 2): Drivetrains, 2013: http://www.hybridcenter.org/hybrid-center-how-hybrid-cars-work-under-the-hood-2.html.

This section of the description ends with a brief conclusion.

Figure 14.5 shows an excerpt from a set of specifications for Logitech headphones.

Figure 14.6: Figure 14.5 Specifications

Source: Logitech, 2012: http://logitech-en-amr.custhelp.com/app/answers/detail/a_id/33976/~/logitech-ue-9000-wireless-headphones-technical-specifications.

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An important kind of description is called a specification. A typical specification (or spec) consists of a graphic and a set of statistics about the device and its performance characteristics. Specifications help readers understand the capabilities of an item. You will see specifications on devices as small as transistors and as large as aircraft carriers.

Because this web-based spec sheet accompanies a consumer product, the arrangement of the specs is geared toward the interests of the likely purchasers. The audio specs are presented before the power specs because potential purchasers of high-end headphones will be most interested in the sound quality.

Figure 14.6 is a description of the process of turning biomass into useful fuels and other products.

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Figure 14.7: Figure 14.6 An Effective Process Description

Source: U.S. Department of Energy, 2013: www1.eere.energy.gov/bioenergy/pdfs/biochemical_four_pager.pdf.

This description begins with an overview of the process of biochemical conversion: the process of using fermentation and catalysis to make fuels and products.

The description includes a flowchart explaining the major steps in the process. The designers included photographs to add visual interest to the flowchart.

The lettered steps in the flowchart correspond to the textual descriptions of the steps in the process.

Most of the description is written in the passive voice (such as “Feedstocks for biochemical processes are selected . . .”). The passive voice is appropriate because the focus of this process description is on what happens to the materials, not on what a person does. By contrast, in a set of instructions the focus is on what a person does.