Memo

The word "memo" is a shortening of "memorandum," from the Latin memorandum, meaning "a thing to be remembered." The full phrase in Latin was memorandum est, "it should be remembered."1 In diplomatic and legal usage dating to the fifteenth century, a memorandum was a note recording something that needed to be recalled at a later date, typically for official purposes.

The internal business memo, a short written communication circulated within an organization, emerged in the early twentieth century as corporations grew too large for verbal instructions to reach everyone who needed them.2

The format standardized quickly: a header listing To, From, Date, and Subject, followed by a body that delivered the message without the ceremonial openings and closings required by a letter. The structure was designed for speed and clarity inside an organization, not for communication with outsiders.3

The memo also served a less obvious purpose. Putting an instruction or decision in writing created a record. That record could protect the writer if a decision went wrong, demonstrate that a warning had been issued, or establish precedence. The phrase "put it in a memo" became shorthand for creating a paper trail.4

Email largely replaced the paper memo in the 1990s, but the format survived intact. The "To," "From," "Date," and "Subject" fields of an email message replicate the memo header exactly. The medium changed. The organizational logic did not.5