A more thorough explanation:

Definition: A formulary is a collection of forms or a list of drugs that are approved for use by a healthcare organization or insurance provider.

Example 1: In the past, a formulary referred to a collection of legal forms used in litigation, such as writ forms kept by the Chancery.

Example 2: Today, a formulary is commonly used in healthcare to refer to a list of drugs that are covered by Medicare or a health-maintenance organization. For example, a health insurance provider may have a formulary that lists the drugs that they will pay for, and patients may need to choose drugs from this list to receive coverage.

Both examples illustrate the definition of a formulary as a collection or list of approved items. In the legal context, a formulary was a collection of approved legal forms, while in healthcare, a formulary is a list of approved drugs.