Legal Definitions - inclusio unius est exclusio alterius

inclusio unius est exclusio alterius is a Latin legal maxim that translates to "the inclusion of one is the exclusion of the other." This principle is a rule of interpretation used in law, particularly when analyzing statutes, contracts, or other legal documents. It suggests that when a document explicitly lists certain items, conditions, or parties, it implies that any items, conditions, or parties not explicitly mentioned were intentionally excluded.

This principle helps courts and legal professionals understand the precise scope and intent of a written rule or agreement, assuming that if something was meant to be included, it would have been stated.

• Scenario: A Residential Lease Agreement

  A lease agreement for an apartment complex states, "Tenants are permitted to have one small dog (under 20 lbs) or one cat."

  Explanation: By explicitly listing "one small dog (under 20 lbs)" and "one cat" as permissible pets, the principle of inclusio unius est exclusio alterius suggests that all other types of pets—such as large dogs, birds, reptiles, or multiple pets of any kind—are implicitly prohibited. If the landlord had intended to allow other animals, they would have included them in the specific list.

• Scenario: A City Ordinance

  A city ordinance regarding public park usage declares, "The use of skateboards, rollerblades, and bicycles is prohibited on the walking trails within City Park."

  Explanation: This ordinance specifically names skateboards, rollerblades, and bicycles as prohibited items on the walking trails. Applying inclusio unius est exclusio alterius, it implies that other forms of personal transportation not listed, such as wheelchairs, strollers, or even electric scooters (if not covered by a broader definition), are not subject to this specific prohibition on the walking trails. The explicit mention of certain items excludes others.

• Scenario: A Company's Employee Benefits Policy

  A company's employee handbook states, "Employees are eligible for tuition reimbursement for courses directly related to their current role in the departments of Engineering, Product Development, or Sales."

  Explanation: The policy explicitly lists three specific departments (Engineering, Product Development, Sales) where role-related courses qualify for tuition reimbursement. According to inclusio unius est exclusio alterius, this implies that employees in other departments, such as Marketing, Human Resources, or Finance, are *not* eligible for tuition reimbursement under this particular policy, even if their courses are directly related to their roles. The specific inclusion of certain departments excludes others.