What is the notation used to indicate something is enclosed in the envelope with the letter or memo?

The term used to indicate that something is enclosed within an envelope along with a letter or memo is "Enclosure." This notation clearly informs the recipient that additional materials are included with the correspondence, which may be relevant or necessary for understanding the context of the letter. It serves as a prompt for the reader to look for and review the attached documents, ensuring that all relevant information is communicated effectively.

Other terms, such as "Closure," typically refer to the formal ending of a document or communication, "Attachment" usually applies to electronic documents that accompany an email or digital correspondence, and "Appendix" indicates supplementary material that is included at the end of a document rather than being enclosed with a letter. Thus, "Enclosure" is the most appropriate term in this context to denote materials included with a physical letter or memo.