Foreword

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This document was prepared by Technical Committee ISO/TC 114, Horology, Subcommittee SC 9, Technical definitions.

This third edition cancels and replaces the second edition ( ISO 6426-2:2002 ), which has been technically revised. It also incorporates the Amendment ISO 6426-2:2002/Amd.1:2012 and the Technical Corrigendum ISO 6426-2:2002/Cor.1:2003 .

The main changes compared to the previous edition are as follows:

some new definitions were added;
some definitions were modified;
the standard’s structure was modified;
Table 1 was moved as a new Annex A.

A list of all parts in the ISO 6426 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 .

Introduction

This document provides technical and commercial definitions in horology; ISO 6426-1 gives technical and scientific definitions, mainly relating to the rate of the time-measuring instrument.

The definitions given in this document, intended more particularly for the general public, have been simplified, especially with regard to terms concerning the rate of a time-measuring instrument.

Where there is ambiguity, it is advisable to refer to the definitions of the corresponding terms in ISO 6426-1 , which are more detailed.

Terms that do not give rise to any confusion, and which occur in other specialized documents, have not been included in this document.

1 Scope

This document defines the principal terms used in horology.

The terms and definitions apply to time-measuring instruments and related devices.

2 Normative references

3 Terms and definitions

4 Terms related to time

5 Terms related to time-measuring instruments

6 Terms related to essential devices and parts

6.1 Power supply

6.2 Time base

6.3 Display

7 Terms related to functions (see Annex A)

7.1 Display of time

7.2 Chronograph

7.3 Alarm

7.4 Calendar

7.5 Other functions

7.6 Additional functions for smartwatches

8 Terms related to components

8.1 Movement components

8.2 Casing components

9 Terms related to accuracy of a time-measuring instrument

Bibliography

ISO 6426-2:2026

Horological vocabulary — - Part 2: Technical and commercial definitions

Current

Published:

20 Feb 2026

1 Scope