Certain shared knowledge is so fundamental that we do not feel the need to articulate or explain it for fear of stating the obvious. However, the design of a new Nomenclature means that the most basic elements of language may need to be examined and defined.

So it was during the drafting of the Harmonised System at the Nomenclature Committee’s 33^rd session in 1973 when discussion centred on the scope of the terms ‘and’ and ‘or’. What did they mean?

" [...] it was agreed that there were instances in the Nomenclature of the conjunctions "and" and "or"　not being employed in accordance with the tacit rules governing their use and that advantage should be taken of the work on the Harmonized System to remedy this by applying the following rules:

1. the conjunction "AND" should normally be used where the texts relate to a list of products (specified by substantives);
2. "OR" should normally be used when the texts indicate the state, qualities or, for example, use of the goods (use of adjectives or adjectival forms);
3. where the conjunction "AND" indicates a mandatory cumulative condition, this condition should be emphasised by using a supplementary term such as "both".

In the Harmonized System, contrary to the popular saw, some things are best NOT left unsaid.