ISO 18173:2026

Non-destructive testing — General terms and definitions

This document defines general technical terms 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: Published
• Publication Date: 08-Jun-2026
• 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: 6060 - International Standard published
• Start Date: 09-Jun-2026
• Due Date: 02-Feb-2026
• Completion Date: 09-Jun-2026

Relations

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

Overview

ISO 18173:2026 - Non-destructive testing - General terms and definitions is an international standard developed by the International Organization for Standardization (ISO). This document provides harmonized definitions of essential technical terms used across multiple non-destructive testing (NDT) disciplines. By establishing a unified vocabulary, ISO 18173:2026 enables clearer communication and more consistent application of NDT methods within global industries such as manufacturing, construction, aerospace, and energy.

Clear and precise terminology is vital for effective collaboration between manufacturers, inspectors, regulatory bodies, and all stakeholders using NDT. The standard supports consistency in interpreting results, compliance with standards, and best practices in quality control.

Key Topics

ISO 18173:2026 covers a range of fundamental terms and concepts for non-destructive testing. Key topics include:

• Acceptance criteria & acceptance level: Definitions for thresholds and parameters used to assess the acceptability of test objects.
• Discontinuity, flaw, and imperfection: Terminology for describing deviations, interruptions, or imperfections in a test object.
• Detection, detection sensitivity, and detection threshold: Concepts central to evaluating the ability of NDT methods to identify and characterize flaws.
• Indication types (relevant, non-relevant, false): Standardized language for categorizing NDT results and their significance.
• NDT methods, techniques, and procedures: Clarification of the hierarchy and relationship between various NDT processes.
• Calibration, standardization, and reference blocks: Terms relating to ensuring the repeatability and reliability of NDT measurements.
• Signal-to-noise ratio and resolution: Concepts critical to the accurate identification and sizing of defects.
• Recording, sizing, and evaluation: Definitions to support documentation and assessment of non-destructive test results.

These terms form the general technical foundation needed for practitioners of non-destructive testing and are not always defined within method-specific standards.

Applications

The standardized terminology in ISO 18173:2026 is beneficial in diverse practical applications:

• Quality assurance: Facilitates consistent interpretation of NDT results, supporting better quality management and defect assessment.
• Compliance and procurement: Provides universally accepted definitions for contract documentation, inspection protocols, and regulatory compliance.
• Training and certification: Supports NDT personnel in gaining a clear understanding of commonly used terms, aiding programs aligned with ISO requirements.
• Cross-industry communication: Enables efficient collaboration and reduces misunderstandings across international supply chains and multi-disciplinary teams.
• Development of method-specific standards: Serves as a reference for drafting, revising, and harmonizing further standards in NDT disciplines-such as ultrasonic, radiographic, and magnetic particle testing.

Organizations adopting ISO 18173:2026 benefit from improved clarity, reduced risk of errors, and enhanced reliability in non-destructive testing activities.

Related Standards

To support comprehensive understanding and implementation, the following related standards and resources are recommended:

• EN 1330-2 - Non-destructive testing - Terminology
  European standard offering complementary definitions in NDT.
• ASTM E1316 - Standard Terminology for Nondestructive Examinations
  Widely used terminology standard from ASTM International.
• ISO/IEC Directives, Part 1 and Part 2
  Procedures and editorial rules for the development and maintenance of ISO standards.
• ISO Online Browsing Platform
  Central repository for ISO terms and definitions in standardization (https://www.iso.org/obp).
• IEC Electropedia
  Online resource for electrical and electronic terminology (https://www.electropedia.org/).

By referencing ISO 18173:2026 together with these related standards, organizations and professionals ensure a robust, standardized approach to non-destructive testing terminology and practice.

Standards Content (Sample)

International
Standard
ISO 18173
First edition
Non-destructive testing — General
2026-06
terms and definitions
Essais non destructifs — Termes généraux et définitions
Reference number
© ISO 2026
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
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Phone: [phone]
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Website: www.iso.org
Published in Switzerland
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1

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
has been established has the right to be represented on that committee. International organizations,
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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).
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)
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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.
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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
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
International Standard ISO 18173:2026(en)
Non-destructive testing — General terms and definitions
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