What does “perishable” typically refer to in mail categories?

The term “perishable” in the context of mail categories specifically refers to items that can decay, spoil, or require specific conditions to maintain their quality, such as refrigeration. This definition aligns predominantly with perishable goods like food products, which have a limited shelf life and can deteriorate quickly if not kept under the proper environmental conditions. In mail processing and delivery, understanding what constitutes perishable items is crucial for ensuring they are handled and delivered in a timely manner to prevent spoilage.

The other options represent different categories of mail but do not capture the essence of what “perishable” means. Documents and letters do not have decay concerns; oversized packages refer to size and weight specifications rather than spoilage; and while time-sensitive mail is important, it does not necessarily imply that the items can spoil or require refrigeration. Thus, the correct understanding of perishable items is pivotal for effective handling in postal services.