"You are what you eat" is a dictum, and so is a law requiring you to curb your dog. A dictum is a formal pronouncement, a rule, or a statement that expresses a truth universally acknowledged.

Dictum dates from the 16th Century. It descended from a Latin word that means "something said." In contemporary use, it means more like "something that is officially said." If the principal of your school issues a dictum declaring "no jeans in school," it's time to go shopping.

Definitions of dictum

n an authoritative declaration

pronouncement, say-so
a pronouncement encouraging or banning some activity
Presidential Directive
a directive issued by the President of the United States; usually addressed to all heads of departments and agencies
Type of:
a statement that is emphatic and explicit (spoken or written)

n an opinion voiced by a judge on a point of law not directly bearing on the case in question and therefore not binding

obiter dictum
Type of:
judgement, judgment, legal opinion, opinion
the legal document stating the reasons for a judicial decision

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