Толковый словарь английского языка - memorandum

noun (plural -dums or memoranda) Etymology: Middle English, to be remembered, from Latin, neuter of memorandus, gerundive of memorare Date: 15th century an informal record, an informal written note of a transaction or proposed instrument, 3. an informal diplomatic communication, a usually brief communication written for interoffice circulation, a communication that contains directive, advisory, or informative matter, Usage: Although some commentators warn against the use of memoranda as a singular and condemn the plural memorandas, our evidence indicates that these forms are rarely encountered in print. We have a little evidence of the confusion of forms, including use of ~ as a plural, in speech (as at congressional hearings). As plurals memoranda and ~s are about equally frequent.