Technical definition

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

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

Parenthetical definitions
Sentence definitions
Extended definitions

Parenthetical definitions

Parenthetical definition are used to introduce words by using a synonym or short description immediately after the word. The synonym or description usually delimited by parenthesis (hence the definition) or commas.

Examples

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

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

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

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. Some more complex definitions in mathematics require an extended definition in which variables are declared (e.g., let x be a real number...) and then restricted by conditions (often using the phrase such that) and quantified using the universal or existential quantifiers (for all ( $\forall$ ) or there exists ( $\exists$ )). In mathematical definitions, convention dictates the use of the word if between the term defined and the definition even though if and only if is generally intended semantically.

Examples

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