Technical definition

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A technical definition is a definition in technical communication describing or explaining technical terminology. Technical definitions are used to introduce the vocabulary which makes communication in a particular field succinct and unambiguous. (For example, the iliac crest from medical terminology is the top ridge of the hip bone. (See ilium.))

Types of technical definitions[edit]

There are three main types of technical definitions.[1]

  1. Parenthetical definitions
  2. Sentence definitions
  3. Extended definitions


Aniline, a benzene ring with an amine group, is a versatile chemical used in many organic syntheses.

The genus Helogale (dwarf mongooses) contains two species.

Sentence definitions[edit]

These definitions generally appear in three different places: within the text, in margin notes, or in a glossary. Regardless of position in the document, most sentence definitions follow the basic form of term, category, and distinguishing features.


A major scale is a diatonic scale which has the semitone interval pattern 2-2-1-2-2-2-1.

  • term: major scale
  • category: diatonic scales
  • distinguishing features: semitone interval pattern 2-2-1-2-2-2-1

In mathematics, an abelian group is a group which is commutative.

  • term: abelian group
  • category: mathematical groups
  • distinguishing features: commutative

Extended definitions[edit]

When a term needs to be explained in great detail and precision, an extended definition is used. They can range in size from a few sentences to many pages. Shorter ones are usually found in the text, and lengthy definitions are placed in a glossary. Relatively complex concepts in mathematics require extended definitions in which mathematical objects are declared (e.g., let x be a real number...) and then restricted by conditions (often signaled by the phrase such that). These conditions often employ the universal and/or existential quantifiers (for all (), there exists ()).

Note: In mathematical definitions, convention dictates the use of the word if between the term to be defined and the definition; however, definitions should be interpreted as though if and only if were used in place of if.


Definition of the limit of a single variable function:

Let be a real-valued function of a real variable and , , and be real numbers. We say that the limit of as approaches is (or, tends to as approaches ) and write if, for all , there exists such that whenever satisfies , the inequality holds.


  1. ^ Johnson-Sheehan, R: "Technical Communication Today", pages 507-522. Pearson Longman, 2007