Harmonised standard

The precise meaning is a legal mechanism. Under the EU's New Approach, legislation states essential requirements, the Commission requests supporting standards from the European standardisation bodies, and once a resulting standard is cited in the Official Journal it becomes harmonised: using it creates the legal presumption that the essential requirements are met. The standard stays voluntary; the presumption is what you buy by following it. Construction products, machinery and pressure equipment all run on this machinery.

The looser meaning — standards aligned between countries — describes a broader family: international standards adopted identically as national ones, interstate standards shared across the CIS, bilateral equivalence arrangements. Alignment reduces the translation cost of cross-border work, which is why everyone pursues it.

The trap in both senses is assuming harmonised means identical in effect. Harmonised European standards still interact with national annexes and national implementations; adopted international standards acquire national deviations. Harmonisation narrows the differences; it rarely eliminates them, and the residue is exactly where cross-border designs get comments.