To define is to determine with precision or to exhibit clearly the boundaries thereof.

Explanation

(English-origin maxim.) A definition must fix the boundaries of the thing defined with precision and clarity — a definition that leaves doubt is no definition at all.

Where this applies

• A zoning board tries to enforce a rule against "commercial activity" without defining what counts as commercial — the definition is useless because it doesn't set clear boundaries.
• A statute creates a new tax on "luxury items" but never specifies what qualifies as a luxury — the law fails to define with precision, leaving everyone guessing.
• A court order requires a company to stop "unfair practices" without specifying which practices — the vague definition gives the company no clear boundary to follow.