What Is a Definition?

The meaning of a term, formally stated. The term may be a single word, or an expression with two or more words.

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Why Do Communicators Need to Define Terms?

To provide readers with the precise meaning of a term. In some cases, readers don't know what the term means, and cannot understand a passage without your providing the definition.

In other instances, readers might be familiar with the term, but not with the specific meaning that you have for it. Some terms, for example, have several meanings. A definition clarifies the meaning you intend to use. Readers may only have a passing understanding of other terms, and the definition provides them with a much-needed reminder.

In other words, clarity in the use of terms is the cornerstone to clarity in all communication efforts. For instance, in the service industry (restaurants, hotels), you can set the expectations of customers by clearly defining what you mean by terms. If you state that a large burger weights 8 ounces before cooking, patrons have a reasonable idea of what size the burger should be when it arrives. In legal documents, defining terms in a contract clarifies the what one party agrees to provide and what another party can expect.

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Which Terms Should You Define?

At the least, define all new technical terms introduced in the communication product, as well as common terms that have a unique meaning in the context of the technical information.

At the most, define all terms that readers might encounter but whose definition they might not remembered.

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The Three Types of Definitions

Pfeiffer (1995) identifies three types of definitions. Each type provides increasing levels of detail.

• In-text definition: A parenthetical phrase that immediately follows the unfamiliar technical term and that sufficiently explains the term so that readers can comprehend the sentence. (A parenthetical phrase is a phrase inside of a sentence that is preceeded and followed by commas, parentheses, or m-dashes (--).)

Example: The instructional designer, the person who plans and develops training courses, had responsibility for leading this meeting.

• Basic definition: A 1- or 2-sentence definition that appears in a list of terms called a glossary or dictionary. If the term is used in more than one, a glossary or dictionary entry might include all of the relevant definitions. If so, the entry will extend beyond 1 or 2 sentences. Each definition is separately numbered.
• Expanded definition: A 1- to 3-paragraph description of the term. It begins with definition in the style of a glossary or dictionary entry, and continues with additional explanatory information. The information may be visual (pictures) or verbal (words), and adds clarity to the brief definition. For example, an expanded definition of a car might include a line drawing of a car and the identification of its key components, such as a steering wheel.

You might incorporate all three types of definitions into a technical communication product. You might include an in-sentence description so readers can continue reading without looking up a term, a glossary entry elsewhere in the communication product and an expanded definition where you describe the term in-depth.

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How to Write Definitions

Provide an in-text definition for each term the first time users encounter it. You do not need to repeat the definition in subsequent passages, if you can assume that readers have completed the earlier passages. (That is, if you are designing a website with several topics, you might define a term the first time it is used in each topic, because you cannot assume that readers have seen the previous topics.

• For basic definition, follow this structured format:
1. Term, usually emphasized with bold type.
2. Part of speech, telling users whether the term is a noun or a verb. This is especially useful information for terms that are familiar to users but are used in unfamiliar ways. Place the part of speech immediately after the term.
3. Definition: One or two sentences that explains the term. The definition need not be a full sentence; it can be a phrase.
4. References to similar terms (called "see also" references) and contrasting terms (called "contrast with" references). Highlight the term in italic type.

For an expanded definition, include all of the components of a basic definition, as well as:

• Expanded description (details that extend beyond the first two sentences).
• Visuals that show what something looks like, especially a physical object.
• Examples, which clarify abstract terms and terms that are similar to other terms.
• Synonyms. Related terms that users should also be familiar with. Begin the list of related terms as "See also." Make sure all of the "see also" terms are in the glossary.

In the expanded defintion, place references to similar terms at the end of the expanded definition.

• Do not include the term being defined, or a variation of the term, in its definition. For example, rather than saying a "a software application is software" you might say "a software application is a type of computer program…."
• Test the draft of a definition with a typical reader to make sure that it is clear.

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Examples

Of an In-text Definition:

Of a Basic Definition:

Of an Expanded Definition

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