Definitions

Sample in Writing Guidelines

In technical writing, defining terms is a task that is often difficult for the writer. However, if terms are not defined adequately, reading may be an even more difficult task for readers. There are three basic types of definitions:

  1. parenthetical
  2. sentence
  3. extended

A parenthetical definition is a brief clarification placed unobtrusively within a sentence.

Examples


The crane is located on the starboard (right) side of the ship.

Corrugated paperboard is the technical term for cardboard.


A sentence definition is a one- or two-sentence clarification which usually follows a standard pattern: the item to be defined (the species) is placed in a category of similar items (the genus) and then distinguished from the other items (by the differentia). For example,

species genus differentia

Hypnoanalysis is a psychoanalytical in which hypnosis technique is used to elicit
unconscious information from a patient.

An electrophorus is an instrument used to generate static electricity.

In sentence definitions it is important to be as specific as possible in writing the genus and differentia. It is even more important to avoid writing circular definitions that merely repeat the key words of the species in the genus or differentia as in: "A required course is a course that is required," or "A balloon mortgage is a mortgage that balloons."  When writing a sentence definition be sure that the genus contains a noun or noun phrase rather than a phrase beginning with when, what, or where.

incorrect

A thermometer is what is used to measure temperature.

correct

A thermometer is a device used to measure temperature.

An extended definition is a long (one- or several-paragraph) detailed clarification of an object, process, or idea. Often an extended definition begins with a sentence definition, which is then elaborated. An extended definition builds on the initial definition which answers the question "What is it?" by answering other questions a reader might have about the term or concept. Some common questions include:

What is it similar to?
What does it look like?
What are its physical features?
What are its distinguishing characteristics?
What are its components?
What does it do?
How does it work?
Who uses it?
What is the relevant background in development or application?
What are examples of its use?
How does it differ from similar objects?
What is its value?

There is no one way to extend a definition, but often one of the following techniques will work effectively:

  1. exemplification
  2. etymology
  3. description of operation
  4. comparison and contrast
  5. analogy
  6. negation
Engineering Communications was last updated May 15, 2000
by webmasters César Meraz and Chantal Tetreault
Copyright 2000