Plural of “memorandum”

The plural of memorandum is memoranda (some dictionaries also accept memorandums).

Why

"Memorandum" is Latin for "a thing to be remembered," a gerundive form of "memorare" (to remind), and it follows the standard Latin neuter -um/-a pattern, giving "memoranda," the same pattern seen in "datum/data" and "curriculum/curricula."

"Memorandums" is widely accepted in everyday business and legal writing, and the shortened form "memo" (which pluralizes fully regularly as "memos") has become so dominant in casual office speech that many English speakers rarely encounter the full word "memorandum" at all outside formal legal or government contexts. Diplomatic writing has its own specific convention worth noting: a "memorandum of agreement" between two governments is a formal document type distinct from, though related to, the more general business "memorandum of understanding," and both terms pluralize identically as "memoranda" or "memorandums" in institutional writing about multiple such agreements. Corporate legal departments in particular tend to default to "memoranda" specifically in contract language, reserving the more casual "memorandums" for internal, non-binding communications where the formal Latin plural would feel unnecessarily stiff.

Usage note

Legal writing, where "memorandum" retains its fullest and most formal use (a "memorandum of understanding," a legal "memorandum" filed with a court), leans more toward "memoranda" as the expected, professional-sounding plural, while general office and business communication uses "memorandums" and "memos" interchangeably without any sense of formality mismatch.

The clipped form "memo" is now so entrenched in everyday office English that it functions almost as a separate word from "memorandum" in practice — nobody would say "I got a memorandum from my boss" in casual speech, reserving the full Latin form for genuinely formal legal, diplomatic, or governmental writing where its weightier register fits the occasion. It's worth noting that the shortened "memo" has essentially replaced "memorandum" so completely in spoken office English that many younger workers encounter the full word "memorandum" for the first time only in a legal or academic context, rather than in everyday workplace conversation where "memo" and "memos" now dominate almost entirely. Government agencies in particular tend to standardize on one plural or the other in their own internal style manuals, so writers producing official correspondence should check the specific agency's preferred convention rather than assuming either form is universally accepted.

Common real mistakes

Writers occasionally use "memorandas," mistakenly adding an English -s to the already-plural Latin form "memoranda" — the correct plural needs no further ending, exactly the same error pattern that occasionally shows up with "medias" for "media." A further mistake worth flagging: some writers use "memorandum" as if it were itself a verb ("to memorandum someone"), an error stemming from confusing the noun with the unrelated, fully regular verb phrase "to send a memo."

The wider pattern

"Memorandum/memoranda" shares the same Latin -um/-a pattern as "datum/data" and "curriculum/curricula," and like "curriculum," it has developed a fully accepted regularized English plural that dominates in less formal registers.

Examples

• The department issued a memorandum outlining the new policy.
• Several memoranda circulated before the final decision was made.
• Legal teams exchanged memorandums throughout the negotiation.
• The court reviewed multiple memoranda filed by both sides.
• A brief memorandum summarized the meeting's key outcomes.
• Internal memorandums often go unread by half the staff.
• The two companies signed a memorandum of understanding.
• Dozens of memoranda from that era have survived in the archive.
• The lawyer drafted a memorandum supporting the motion.
• Staff received a memorandum reminding them of the deadline.
• The ambassador reviewed several memoranda before the treaty negotiations resumed.
• New hires receive a memorandum outlining company policy on their first day.
• The general counsel filed a confidential memorandum summarizing potential legal exposure.
• Employees were asked to acknowledge receipt of the updated safety memorandum.
• The two firms drafted competing memoranda ahead of the merger talks.