A dietary requirement is what a guest can and cannot eat. Note the dietary requirement, a serious dietary requirement.
Allergy and preference are both covered by the phrase and are not the same thing at all, which is why kitchens ask which it is. A dietary requirement given at booking is far easier to meet than one given at the table.
1noundietary requirementWhat a guest can and cannot eat.
“Four of the party had a dietary requirement and none had mentioned it.”
dietary requirement is a requirement.
Practised in Restaurant & Cafe