written communication sent within a company or government, typically bearing an advisory or informative message and intended for informal record-keeping;
e.g. He left a memorandum with instructions for the people who he supervised at work.
(noun)
a note made as a record for the future;
e.g. They signed a memorandum of partnership.
(noun)
a document that records the details of a contract or agreement;
e.g. Harvey and Louis composed a memorandum of by-laws for everyone at the firm.