ISO 22745-11:2010(E)

8 Guidelines for the formulation of definitions in English

8.1 General

The guidelines in Clause 8 apply to definitions written in English. They shall be applied to a definition in another language to the extent that they are consistent with the rules of grammar and the common usage of that language.

The guidelines in Clause 8 apply only to terms for classes.

8.2 Structure of a definition

Each definition shall describe the concept in the form of a logical pattern consisting of a subject field or domain, followed by essential characteristics that provide an understanding of the concept. The definition shall include delimiting characteristics that serve to distinguish the concept from other similar or closely-related concepts.

NOTE   This is called an intensional definition, a definition that describes the intension of a concept by stating the superordinate concept and the delimiting characteristics.

EXAMPLE   The following is an example of an intensional definition for the concept incandescent lamp:

incandescent lamp

electric lamp in which a filament is heated by an electric current in such a way that it emits light

[ISO 1087-1]

8.3 Format of a definition

A definition shall start with a word in lower case (except for acronyms and proper nouns, which must always be capitalized) and end without a period. A definition shall not contain multiple sentences.

In many cases, the material in sentences following the initial phrase serves to explain or clarify the meaning of the initial phrase. Such material shall be put in notes or examples. If more than one sentence is truly needed to unambiguously define the meaning of a term, supporting terms shall be created.

See ISO 704 for the formulation of definitions and underlying principles.

The following basic principles shall apply to the drafting of definitions:

  1. The definition shall have the same grammatical form as the term. Thus, to define a noun, a basic term or noun phrase shall be used; to define a singular noun, the singular shall be used.

  2. The definition shall consist of a basic part stating the generic concept to which the concept belongs and another part enumerating the characteristics that distinguish the concept from coordinate concept.

  3. The definition shall not begin with an expression such as "term used to describe" or "term denoting" nor take the form "[term] is..." or "[term] means..."

  4. Unless there is a specific reason, the definition shall not begin with an article.

  5. The definition of a quantity shall be formulated in accordance with the provisions of ISO 80000-1:2009, clause 4. This means that a derived quantity may be defined by means of other quantities only. Units shall not be used in the definition of a quantity.

NOTE   Items a), c) and d) are derived from the principle of substitution (see 6.2).

EXAMPLE   The following is a pair of acceptable and unacceptable definitions.

Acceptable Unacceptable

pressure

quotient of force on a surface and area of that surface

pressure

force per unit area of surface

Images may be used as explanations if necessary. They do not, however, replace a verbal definition.

8.4 Self reference

A term shall not be included in the definition of the concept (self referencing).

EXAMPLE 1  The following is a pair of acceptable and unacceptable definitions.

Acceptable Unacceptable

resistor

electrical device with two terminals, characterized essentially by its electrical resistance

NOTE Adapted from IEV.

resistor

set of resistors of which each resistor can be described with the same group of data element types

NOTE Resistors are devices used because of their primary property of resistance.

EXCEPTION When the term completely and unambiguously defines the concept (e.g., a structural name for a chemical or a drug), the term may be used as the definition.

EXAMPLE 2  The following is a pair of acceptable and unacceptable definitions.

Acceptable Unacceptable

n-(4-hydroxyphenyl)acetamide

n-(4-hydroxyphenyl)acetamide

n-(4-hydroxyphenyl)acetamide

a synthetic chemical used as an analgesic and as an antipyretic, whose generic name is "acetaminophen"

8.5 Definitions associated with specific concepts

When a generic relation exists between two concepts and the term for the specific concept is a qualification of the term for the generic concept, it is recommended that the definition of the specific concept be in terms of the generic concept.

EXAMPLE   Suppose the following concept is defined:

resistor

electrical device with two terminals, characterized essentially by its electrical resistance

NOTE Adapted from IEV.

Then the second of the following definitions is recommended.

Not recommended

adjustable resistor

electrical device with two terminals, characterized essentially by its electrical resistance, whose overall ohmic value is fixed during use, and which has one or more movable terminals designed to be set and fixed prior to use to include any desired value of resistance within the range of the complete resistor

NOTE The opposition to the flow of current is an inherent property of the material used and is manifest in the heat dissipated from the item itself.

Recommended

adjustable resistor

resistor whose overall ohmic value is fixed during use, and which has one or more movable terminals which are designed to be set and fixed prior to use to include any desired value of resistance within the range of the complete resistor

NOTE The opposition to the flow of current is an inherent property of the material used and is manifest in the heat dissipated from the item itself.

8.6 Definitions associated with complex terms

When a term is formulated as a complex term the definition shall describe the concept as a whole without reference to a superordinate concept.

EXAMPLE   The following is a pair of acceptable and unacceptable definitions.

Acceptable Unacceptable

recorder-simulator

single component with the dual function of providing synthetic signals and making a permanent representation of these signals in a form suitable for analysis

recorder-simulator

recorder that also provides synthetic signals

8.7 Use of dimensions in definitions

When a non-metric dimension is included in a definition, its metric equivalent shall follow in parentheses.

EXAMPLE   The following is a pair of acceptable and unacceptable definitions.

Acceptable Unacceptable

power-driven floor sander

sander specifically designed for the purpose of smoothing the surface of wood floors, with the exception of the portion within one or two inches (25.4 mm or 50.8 mm) of the wall

power-driven floor sander

sander specifically designed for the purpose of smoothing the surface of wood floors, with the exception of the portion within one or two inches of the wall

8.8 Use of capital letters in definitions

Only acronyms, proper nouns, words reflecting titles, and letters reflecting symbols shall be capitalized.

EXAMPLE   The following are pairs of acceptable and unacceptable definitions.

Acceptable Unacceptable

U-bolt

bolt bent approximately 180 degrees (3.141 radians) in the shape of the letter U and with both ends threaded

U-bolt

bolt bent approximately 180 degrees (3.141 radians) in the shape of the letter u and with both ends threaded

DDT insecticide

insecticide containing DDT as the active ingredient

DDT insecticide

insecticide containing ddt as the active ingredient

NOTE   The definition "insecticide containing DDT as the active ingredient" is acceptable only if an entry in the allowable abbreviation list (see 10.3) exists with abbreviated name equal to "DDT".

8.9 Use of abbreviations in definitions

A definition shall not contain an abbreviation or acronym unless an entry in the allowable abbreviation list (see 10.3) exists with abbreviated name equal to the abbreviation or acronym.

EXAMPLE   The following is an example of the use of an abbreviation.

DDT insecticide

insecticide containing DDT as the active ingredient

NOTE   The above definition is valid provided that "DDT" is in the allowable abbreviation list (see 10.3).

8.10 Excluded concepts

When a concept being defined may be easily confused with a similar concept, the definition may explicitly state that the similar concept is excluded.

NOTE 1  The list of excluded concepts need not be exhaustive.

NOTE 2  If there is more than one definition associated with a concept, each definition may have a different list of excluded concepts.

EXAMPLE   The concept wire-wound fixed resistor may be easily confused with the concept ignition interference suppressor. Therefore, the following definition is created:

wire-wound fixed resistor

resistor whose ohmic value cannot be adjusted or varied and whose resistance element consists of high resistance wire or ribbon either wound on an insulated form or constructed so as to be self-supporting

NOTE Opposition to the flow of current is an inherent property of the resistance wire and is manifest by the heat dissipation from the resistor.

EXCLUDES ignition interference suppressor

NOTE 3  The exclusion relationship is not symmetric.

8.11 Included concepts

When it helps to clarify the meaning of a concept, the definition may explicitly state that the certain subordinate concepts are included.

NOTE 1  The list of included concepts need not be exhaustive.

NOTE 2  If there is more than one definition associated with a concept, each definition may have a different list of included concepts.

EXAMPLE   It may not be obvious to a casual reader that the concept of telephone set includes the concept of wall telephone. In order to make this relationship clearer, the following definition is created:

telephone set

combination of items consisting of a handset or telephone, a switch and its associated wiring, with self-contained or separate ringer box

INCLUDES wall telephone

8.12 Synonyms

All known names for a concept shall be attached to the concept by instances of term. When more than one term is associated with a concept, these names are considered to be in synonymy.

EXAMPLE   The terms photo semiconductor device and photoelectric cell are synonymous. Therefore, they are both attached to the same concept. photo semiconductor device is the preferred name. This would be rendered as follows:

photo semiconductor device

photoelectric cell

semiconductor device that is responsive to visible or infrared radiant energy

NOTE May or may not include mounting hardware and/or heat sink.

EXCLUDES diode semiconductor devicethyristor semiconductor device

8.13 Markup

Definitions should be marked up in XML to enable processors to identify, search for, and display components of the definition described in Clause 8. References to included concepts (see 8.10), excluded concepts (see 8.10), and synonyms (see 7.7) should be included as specific elements of the markup.

NOTE   See Annex C for guidance on rendering definitions.


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