ISO 18173

Non-destructive testing — General terms and definitions

ISO/TS 18173:2005 defines the general technical terms that are used in many non-destructive testing disciplines.

Essais non destructifs — Termes généraux et définitions

L'ISO/TS 18173:2005 définit les termes techniques généraux qui sont utilisés dans de nombreuses disciplines d'essais non destructifs.

General Information

• Status: Not Published
• ICS: 01.040.19 - Testing (Vocabularies)
• ICS: 19.100 - Non-destructive testing
• Technical Committee: ISO/TC 135 - Non-destructive testing
• Drafting Committee: ISO/TC 135 - Non-destructive testing
• Current Stage: 6000 - International Standard under publication
• Start Date: 01-May-2026
• Completion Date: 02-May-2026

Relations

• Revises: ISO/TS 18173:2005 - Non-destructive testing — General terms and definitions
• Effective Date: 06-Jun-2022

Overview

ISO/FDIS 18173 (Non-destructive testing - General terms and definitions) is an international standard developed by ISO/TC 135. This standard establishes the key technical terms and definitions widely used in many non-destructive testing (NDT) disciplines. By providing a unified vocabulary, ISO/FDIS 18173 supports clear communication and consistent interpretation throughout the global NDT community. This standard supersedes ISO/TS 18173:2005 and harmonizes terminology with other significant standards such as EN 1330-2:1998 and ASTM E1316.

Key Topics

• Unified Terminology: The standard defines general terms crucial for understanding and applying NDT techniques across industries.
• Cross-Disciplinary Use: Terms covered are applicable across multiple NDT methods, such as ultrasonic testing, radiographic testing, and magnetic particle testing.
• Clarification of Concepts: Key NDT concepts such as “acceptance criteria,” “discontinuity,” “flaw,” “calibration,” and “signal-to-noise ratio” are clearly defined.
• Foundation for Procedures: Definitions serve as a cornerstone for developing NDT procedures, training materials, and further sector-specific standards.

Selected Example Terms

• NDT method: A discipline applying a physical principle in non-destructive testing (e.g., ultrasonic testing).
• Detection sensitivity: The capacity of an NDT method to reveal discontinuities or imperfections in materials.
• Standardization: The adjustment of NDT instruments using reference blocks to ensure reproducible responses.
• Test object: The part, material, or component subjected to non-destructive evaluation.

Applications

ISO/FDIS 18173 is intended for professionals and organizations involved in the development, application, and regulation of non-destructive testing. Practical applications include:

• Industry Standards: Establishing common language in codes, procedures, and technical documents for NDT.
• Training and Qualification: Providing a consistent foundation for NDT personnel training, certification, and examinations.
• Manufacturing and Quality Assurance: Assisting manufacturers, inspectors, and engineers in accurately communicating test requirements and results.
• International Trade: Supporting compliance and interoperability in global markets by harmonizing NDT terminology.
• Regulatory Compliance: Facilitating reference in national and international regulations concerning safety-critical inspections.

Related Standards

Organizations involved with non-destructive testing may also reference the following related standards:

• ISO/TS 18173:2005 - Previous version, now replaced and updated by ISO/FDIS 18173.
• EN 1330-2:1998 - European standard related to terms used in non-destructive testing.
• ASTM E1316 - Provides terminology for NDT in American practice.
• ISO/IEC Directives - Guidelines governing standards development and terminology consistency.

For a comprehensive list of NDT-related standards, visit the official ISO website.

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ISO/FDIS 18173 is a crucial reference for anyone involved in non-destructive testing, ensuring clarity, efficiency, and reliability across the global NDT industry. By standardizing terms, it significantly reduces miscommunication and supports best practices in safety, quality, and regulatory compliance.

Standards Content (Sample)

FINAL DRAFT
International
Standard
ISO/FDIS 18173
ISO/TC 135
Non-destructive testing — General
Secretariat: JISC
terms and definitions
Voting begins on:
Essais non destructifs — Termes généraux et définitions 2026-03-05
Voting terminates on:
2026-04-30
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
AND TO PROVIDE SUPPOR TING DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO­
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
Reference number
ISO/FDIS 18173:2026(en) © ISO 2026

FINAL DRAFT
ISO/FDIS 18173:2026(en)
International
Standard
ISO/FDIS 18173
ISO/TC 135
Non-destructive testing — General
Secretariat: JISC
terms and definitions
Voting begins on:
Essais non destructifs — Termes généraux et définitions
Voting terminates on:
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
AND TO PROVIDE SUPPOR TING DOCUMENTATION.
© ISO 2026
IN ADDITION TO THEIR EVALUATION AS
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO­
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
or ISO’s member body in the country of the requester.
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland Reference number
ISO/FDIS 18173:2026(en) © ISO 2026

ii
ISO/FDIS 18173:2026(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1

iii
ISO/FDIS 18173:2026(en)
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
has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by ISO/TC 135, Non-destructive testing.
This first edition cancels and replaces the first edition of ISO/TS 18173:2005, which has been technically
revised.
The main changes are as follows:
— harmonizes and updates the terms and definitions of Non-Destructive Testing (NDT) in ISO/TS 18173:
2005, EN 1330-2: 1998 and ASTM E1316-13c.
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
ISO/FDIS 18173:2026(en)
...

ISO/DIS FDIS 18173:2025(en)
ISO/TC 135
Secretariat: JISC
Date: 2025-03-272026-02-19
Non-destructive testing — General terms and definitions
Essais non destructifs — Termes généraux et définitions
FDIS stage
ISO/FDIS 18173:2026(en)
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication
may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying,
or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO
at the address below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: + 41 22 749 01 11
EmailE-mail: [e-mail]
Website: www.iso.orgwww.iso.org
Published in Switzerland
ii
ISO/DIS FDIS 18173:20252026(en)
Contents
Foreword . iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1

Foreword . iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Alphabetical index . 5

iii
ISO/FDIS 18173:2026(en)
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 has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely 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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent rights
in respect thereof. As of the date of publication of this document, ISO had not received notice of (a) patent(s)
which may be required to implement this document. However, implementers are cautioned that this may not
represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents.www.iso.org/patents. ISO shall not be held responsible for identifying any or all such
patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
Field Code Changed
This document was prepared by ISO/TC 135, Non-destructive testing.
This first edition cancels and replaces the first edition of ISO/TS 18173:2005, which has been technically
revised.
The main changes are as follows:
— — this document harmonizes and updates the terms and definitions of Non-Destructive Testing (NDT) in
ISO/TS 18173: 2005, EN 1330-2: 1998 and ASTM E1316-13c.
A list of all parts in the ISO 18173 series can be found on the ISO website.
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.
Field Code Changed
iv
ISO/DIS FDIS 18173:20252026(en)
Introduction
This document defines the general technical terms that are used in many non-destructive testing disciplines.
These terms are not usually defined in the standards pertaining to individual non-destructive test methods.
Thus, the terms and definitions in this document serve to establish a common basis for further standardization
and general use in the field of non-destructive testing and thereby provide for enhanced understanding in
commerce and industry.
v
DRAFT International Standard ISO/DIS 18173:2025(en)

Non-destructive testing — General terms and definitions
1 Scope
This document defines general technical terms used in many non-destructive testing disciplines.
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:
— — ISO Online browsing platform: available at https://www.iso.org/obphttps://www.iso.org/obp
— — IEC Electropedia: available at https://www.electropedia.org/https://www.electropedia.org/
3.1 3.1
...

DRAFT
International
Standard
ISO/DIS 18173
ISO/TC 135
Non-destructive testing — General
Secretariat: JISC
terms and definitions
Voting begins on:
Essais non destructifs — Termes généraux et définitions
2025-05-23
Voting terminates on:
ICS: 01.040.19; 19.100
2025-08-15
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
This document is circulated as received from the committee secretariat.
BE CONSIDERED IN THE LIGHT OF THEIR
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
NATIONAL REGULATIONS.
RECIPIENTS OF THIS DRAFT ARE INVITED
TO SUBMIT, WITH THEIR COMMENTS,
NOTIFICATION OF ANY RELEVANT PATENT
RIGHTS OF WHICH THEY ARE AWARE AND TO
PROVIDE SUPPORTING DOCUMENTATION.
Reference number
ISO/DIS 18173:2025(en)
DRAFT
ISO/DIS 18173:2025(en)
International
Standard
ISO/DIS 18173
ISO/TC 135
Non-destructive testing — General
Secretariat: JISC
terms and definitions
Voting begins on:
Essais non destructifs — Termes généraux et définitions
ICS: 01.040.19; 19.100 Voting terminates on:
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
© ISO 2025
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
STANDARDS MAY ON OCCASION HAVE TO
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
This document is circulated as received from the committee secretariat. BE CONSIDERED IN THE LIGHT OF THEIR
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
or ISO’s member body in the country of the requester.
NATIONAL REGULATIONS.
ISO copyright office
RECIPIENTS OF THIS DRAFT ARE INVITED
CP 401 • Ch. de Blandonnet 8
TO SUBMIT, WITH THEIR COMMENTS,
CH-1214 Vernier, Geneva
NOTIFICATION OF ANY RELEVANT PATENT
Phone: [phone]
RIGHTS OF WHICH THEY ARE AWARE AND TO
PROVIDE SUPPORTING DOCUMENTATION.
Email: [e-mail]
Website: www.iso.org
Published in Switzerland Reference number
ISO/DIS 18173:2025(en)
ii
ISO/DIS 18173:2025(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
Alphabetical index . 4

iii
ISO/DIS 18173:2025(en)
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
has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
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 documents 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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by ISO/TC 135.
This second edition cancels and replaces the first edition (ISO/TS 18173:2005), which has been technically
revised.
The main changes are as follows:
— This standard harmonizes and updates the terms and definitions of Non-Destructive Testing (NDT) in
ISO/TS 18173: 2005, EN 1330-2: 1998 and ASTM E1316-
...