A technical specification, adopted by a recognised standardisation body, for repeated or continuous
application, with which compliance is not compulsory, and which is one of the following:

a) ‘international standard’ means a standard adopted by an international standardisation body;

b) ‘European standard’ means a standard adopted by a European standardisation organisation;

c) ‘harmonised standard’ means a European standard adopted on the basis of a request made by the
Commission for the application of Union harmonisation legislation;

d) ‘national standard’ means a standard adopted by a national standardisation body.

Source: Article 2(1) of Regulation (EU) No 1025/2012, as quoted in NIS2

glossary