Technical definition

Explanation of technical terminology

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 ).

## Types of technical definitions

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

1. Power definitions
2. Secondary definitions
3. Extended definitions

### Examples

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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

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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.

### Examples

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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

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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 ( ∀ {\displaystyle \forall } ), there exists ( ∃ {\displaystyle \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.

### Examples

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Definition of the limit of a single variable function:

> Let  f {\displaystyle f} be a real-valued function of a real variable and  x {\displaystyle x} ,  a {\displaystyle a} , and  L {\displaystyle L} be real numbers. We say that the limit of f {\displaystyle f} as x {\displaystyle x} approaches a {\displaystyle a} is L {\displaystyle L} (or,  f ( x ) {\displaystyle f(x)} tends to L {\displaystyle L} as x {\displaystyle x} approaches a {\displaystyle a} ) and write  lim x → a f ( x ) = L {\textstyle \lim _{x\to a}f(x)=L} if, for all  ϵ > 0 {\displaystyle \epsilon >0} , there exists  δ > 0 {\displaystyle \delta >0} such that whenever  x {\displaystyle x} satisfies  0 < | x − a | < δ {\displaystyle 0<|x-a|<\delta } , the inequality  | f ( x ) − L | < ϵ {\displaystyle |f(x)-L|<\epsilon } holds.

## References

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