ISO 33400:2026

International
Standard
ISO 33400
First edition
Reference materials — Vocabulary
2026-06
Matériaux de référence — Vocabulaire
Reference number
© ISO 2026
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
3.1 General terms .1
3.2 Terms related to reference material production .3
3.3 Terms related to reference material characterization .4
3.4 Terms related to use of reference materials .7
Bibliography . 9
Index . 10

iii
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee
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with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
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This document was prepared by Technical Committee ISO/TC 334, Reference materials.
This first edition cancels and replaces the third edition (ISO Guide 30:2015), which has been technically
revised.
The main changes are as follows:
— order of presentation of the terms and definitions has been revised and regrouped;
— definitions of certified reference material and certified value have been revised;
— definition of indicative value has been revised to be more consistent with the typical characteristics and
intended uses of such values.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
Introduction
Reference materials (RMs) are widely used for the calibration of measuring systems, for the evaluation of
measurement procedures, and for the internal or external quality control of measurements and laboratories.
They can also enable the expression of functional properties in arbitrary units, for instance in certain
cases relevant for biology or material sciences. RMs play an important role in national and international
standardization activities and in the accreditation of laboratories.
This document defines terms used in connection with the production and use of RMs and certified reference
materials (CRMs). It aims to ensure use of consistent terminology by organizations worldwide that work
with RMs and CRMs.
v
International Standard ISO 33400:2026(en)
Reference materials — Vocabulary
1 Scope
This document defines terms related with the production and use of reference materials including certified
reference materials.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— IEC Electropedia: available at http:// www .electropedia .org/
— ISO Online browsing platform: available at http:// www .iso .org/ obp
3.1 General terms
3.1.1
reference material
RM, noun
material, sufficiently homogeneous and stable with respect to one or more specified properties, which has
been established to be fit for its intended use (3.4.1)
Note 1 to entry: The specified properties can be quantitative or qualitative (nominal property (3.3.5) or ordinal
property (3.3.6)).
[1]
Note 2 to entry: ISO/IEC Guide 99:2007 has an analogous definition (5.13).
3.1.2
certified reference material
CRM, noun
reference material (3.1.1) that has at least one certified value (3.1.3)
Note 1 to entry: A certified reference material can also have one or more indicative values (3.1.4).
3.1.3
certified value
certified property value, noun
value, determined by a metrologically valid procedure and accompanied by an uncertainty statement and a
statement of metrological traceability, assigned to a property of a reference material (3.1.1) and identified as
such in the reference material document (3.1.5)
Note 1 to entry: Certified values can be suitable for, for example, calibration of a measurement system, validation of
measurement procedures, assessing precision and/or accuracy of a method, and assessing stability of the composition
of materials to which they are assigned. Additional information on uses of certified values can be found in ISO 33403
[2]
.
Note 2 to entry: In the case of a quantitative property, the uncertainty statement is a reported measurement
[3]
uncertainty. ISO 33405 gives further details of measurement uncertainty and metrological traceability for
quantitative certified values.

Note 3 to entry: In the case of a qualitative (nominal or ordinal) property, the uncertainty statement can be a statement
of confidence, and the statement of metrological traceability refers to the metrological traceability of measured values
used in assigning the qualitative value, together with information on qualitative reference materials or data used in
[4]
assigning the value. ISO 33406:2024 gives further information on statements of confidence and traceability for
qualitative reference materials.
Note 4 to entry: The uncertainty statement for a certified value generally includes contributions from reference
material characterization (3.3.1) and assessment of reference material homogeneity (3.3.8) and reference material
stability (3.3.11).
Note 5 to entry: Examples of metrologically valid procedures for reference material characterization (3.3.1) are
[3]
described in ISO 33405 .
3.1.4
indicative value, noun
information value, noun
value, assigned to a property of a reference material (3.1.1), that does not fulfil all the requirements of a
certified value (3.1.3), but is warranted as suitable for specific purposes as identified in the reference material
document (3.1.5)
Note 1 to entry: Indicative values can be suitable for, for example, comparison of laboratory results with an average
or consensus from other laboratories, use in method harmonization, assessing precision of a method, and assessing
stability of the composition of materials to which they are assigned. Because indicative values do not fulfil all the
requirements of a certified value, they are not usually suitable for use in calibration.
Note 2 to entry: Terms other than those listed can be used to refer to indicative values (e.g., assessed value, informative
value, reference value, and non-certified value).
3.1.5
reference material document
RM document, noun
document containing all the information that is essential for using a reference material (3.1.1)
[5]
Note 1 to entry: The required and recommended content of a reference material document is described in ISO 17034
[6]
and ISO 33401 . For the purposes of this definition, the required content is regarded as information that is essential
for using a reference material (3.1.1).
Note 2 to entry: Reference material producers (3.2.2) can use different terms to describe a reference material document,
including certificate, reference material certificate (3.1.6), certificate of analysis, or product information sheet (3.1.7).
3.1.6
reference material certificate
RM certificate, noun
reference material document (3.1.5) for a certified reference material (3.1.2), stating the certified value (3.1.3)
and confirming that the necessary procedures have been carried out to ensure its validity and metrological
traceability
3.1.7
product information sheet
reference material document (3.1.5) for a reference material (3.1.1) that is not a certified reference material
(3.1.2)
3.1.8
reference material production report
production report, noun
document giving detailed descriptions of all the steps taken in reference material production (3.2.1) of a
reference material (3.1.1) that is not a certified reference material (3.1.2)
Note 1 to entry: Information in a reference material production report can include descriptions of the preparation of
the reference material (3.1.1), methods of measurement, factors affecting accuracy, and statistical treatment of results.

3.1.9
reference material certification report
certification report, noun
document giving detailed descriptions of all the steps taken in reference material production (3.2.1) of a
certified reference material (3.1.2)
Note 1 to entry: Information in a reference material certification report can include descriptions of the preparation
of the certified reference material (3.1.2), methods of measurement, factors affecting accuracy, statistical treatment of
results, and the way in which metrological traceability has been established.
Note 2 to entry: The reference material producer (3.2.2) can include descriptions pertaining to indicative values (3.1.4)
in the reference material certification report.
3.2 Terms related to reference material production
3.2.1
reference material production
RM production, noun
production, noun
activities and tasks that are necessary in the development of a reference material (3.1.1) leading to, and
including, the reference material (3.1.1) becoming available to the user
Note 1 to entry: Necessary activities can include, for example, project planning, material handling and storage,
material processing, assessment of reference material homogeneity (3.3.8), assessment of reference material stability
(3.3.11), reference material characterization (3.3.1), where applicable, assignment of property values and statements of
their uncertainties and metrological traceability, and authorization and issue of a reference material document (3.1.5).
[5]
Note 2 to entry: Requirements for reference material production are described in ISO 17034 .
3.2.2
reference material producer
RM producer, noun
RMP, noun
body that is fully responsible for the reference material production (3.2.1)
Note 1 to entry: The body can be any organization or company, public or private.
3.2.3
subcontractor
body that undertakes selected aspects of reference material production (3.2.1) under its own management
system on behalf of the reference material producer (3.2.2)
Note 1 to entry: Aspects of reference material production that may be subcontracted by the reference material producer
[5]
(3.2.2) are specified in ISO 17034 .
Note 2 to entry: Subcontractors can be paid or unpaid.
Note 3 to entry: Advisors, who can be asked for recommendat
...