And versus or: specify the requirement.
A conjunction can change who qualifies or what a reader must provide. The word “or” may also leave the status of a combined option unstated. A complete instruction should identify whether one option is sufficient and whether both are permitted.
By Adam Frick · First draftA writer can produce a perfectly grammatical instruction that leaves a practical question unanswered. The reader may understand each word but remain unsure which combination satisfies the requirement. A conjunction often sits at the centre of that uncertainty. In instructions, I want the wording to state whether the reader needs both options, at least one option or exactly one option.
Make the combined possibility explicit.
Many buildings have a mixture of natural and mechanical ventilation, with either (or both) systems in different spaces.
The parenthetical phrase “or both” explicitly includes the combined possibility. The reader does not have to decide whether “either” excludes a combination. This published example demonstrates a useful clarification in technical public information. The sentence is descriptive, so the teaching comparisons below use a separate invented requirement.
Compare three different requirements.
The application must include a CV and a cover letter.
The application must include a CV or a cover letter, or both.
The application must include either a CV or a cover letter, but not both.
The first instruction requires two documents. The second accepts either document alone and also accepts a submission containing both. The third excludes a submission containing both documents. Each sentence has a different consequence for the applicant, so replacing “and” with “or” is a change of requirement rather than a stylistic improvement.
Ordinary English does not give “or” one exclusive interpretation in every context. A menu may imply a choice of one item, while an eligibility rule may allow several qualifying routes. The surrounding situation contributes to the interpretation. When compliance matters, spell out the permitted combination instead of relying on that implication.
Give negation extra attention.
Do not submit a CV or a cover letter.
Submit neither a CV nor a cover letter.
Do not submit both a CV and a cover letter.
The first instruction normally prohibits either document, and the second makes that reading explicit. The third prohibits the combination but does not itself require a submission. A writer who intends exactly one document still needs to say that one document is required. The scope of the negative changes the practical meaning of the instruction.
A public-facing rule deserves a quick test against possible submissions. Check the case with neither document, the case with one document and the case with both documents. Confirm that the wording produces the result you intend for every case. This check tests the logic before polishing the language.
My broader recommendation concerns grammatical responsibility. A reader should not need native-speaker intuition to discover which combination a rule permits. Name the requirement, then make the conjunction express that requirement. A few extra words can be worth more than a beautifully short ambiguity.