Origin: Latin suffix -ary
Dietary has 4 different meanings across 2 categories:
a regulated daily food allowance
"The general was ordered to enforce strict dietary limits on his troops during the winter march."
A regulated diet.
"The athlete followed a strict dietary plan to prepare for the marathon."
Of, or relating to diet.
"The dietary guidelines recommend eating more fruits and vegetables every day."
The word dietary comes from the Medieval Latin term diētārium, which originally meant a book prescribing a specific diet. This entered English through its root in classical Latin, where diaeta referred to a regimen of food and drink.