Monthsaries or Monthsarries? The Plural of Monthsary, Explained

You are typing a caption. You want to say something about the eleven months you have been together, and halfway through the word your thumb stops. Monthsaries? Monthsarries? Monthsary's? You delete it, retype it, then give up and write "11 months" instead.

It is a small thing and it happens constantly, which is why the question turns up in search over and over. Here is the short answer, the reason the doubt exists at all, and a set of caption-ready phrasings so you never have to stall on it again.

The plural of monthsary is monthsaries. One r, and the -y becomes -ies exactly the way it does in anniversary to anniversaries, library to libraries, century to centuries.

So: "we have celebrated eleven monthsaries" is correct. "Monthsarries" is not - and neither is "monthsary's", which is a possessive, not a plural. You would only write monthsary's when the monthsary owns something: "the monthsary's whole point is the excuse to dress up."

Because of anniversary. People reach for monthsary as the monthly version of anniversary, and anniversary has a double consonant sitting in the middle of it - the two n's in anni-. Some part of the brain files the word as "the one with the doubled letter" and helpfully doubles the wrong one on the way out.

There is a second reason, and it is more practical: almost nobody learns this word by reading it. You hear it. Spoken aloud, monthsary and monthsarry are identical, so there is no moment where the spelling gets corrected. The first time most people write it down is in a caption at eleven at night, with no reference point at all.

It also does not help that you cannot settle the argument by reaching for a dictionary. Monthsary is a Philippine English coinage - a blend of month and anniversary - and it does not appear in the big print dictionaries like Merriam-Webster or the Oxford English Dictionary, though it is documented in Wiktionary as a Philippine English term. Words that live mostly in speech and social captions do not get a spelling authority handed to them. They get consensus instead, and the consensus here is firmly one r.

If you want a rule you can actually remember at eleven at night: the word is month + (anniv)ersary. The r you keep is the r from -ersary. There is only one of those in anniversary, so there is only one in monthsary.

Spell it out slowly once - m-o-n-t-h-s-a-r-y - and notice there is nothing in there that wants doubling. The h and s sit next to each other and do all the work your ear was attributing to a double r.

Capitalisation trips people up almost as often as the spelling. Monthsary is a common noun, not a proper one, so it does not need a capital M unless it starts the sentence or you are writing a title. "Happy monthsary" is fine. "Happy Monthsary" is fine too in a greeting, the same way "Happy Birthday" is - greetings get a pass. What you do not need is a capital M in the middle of a sentence: "our third monthsary was the best one."

Numbers behave normally as well. First monthsary, 2nd monthsary, 6th monthsary. If you are writing it as a hashtag, the spaces and punctuation disappear but the spelling does not: #happymonthsary, #11thmonthsary.

"More months to come" is the near-universal sign-off on a monthsary post, and it is grammatical exactly as written - it is short for "here is to more months to come." If you want it to read a little less like a template, the fix is specificity rather than different wording: name a month. "Month twelve, and I still have not run out of things to tell you" does more work than any amount of rephrasing.

You will also see "happy us day" used interchangeably with monthsary. Us day is the same idea under a softer name - the monthly date a couple treats as theirs - and it sidesteps the spelling problem entirely, which may be part of its appeal. Both are correct. Pick whichever one sounds like you.

If you want to avoid the word altogether, there are alternatives, and each has its own flavour. Monthiversary is the American coinage, built the same way but keeping more of anniversary intact. Mensiversary is the Latin-purist option, from mensis for month, and it is technically the most defensible and the least used by an enormous margin.

None of them is more correct than the others, because none of them is in the dictionary in the first place. If you are writing for a Filipino audience, monthsary is the one people actually use. We went through all three in more detail in our guide to whether it is [monthsary, monthiversary or mensiversary](/blog/monthsary-monthiversary-mensiversary-correct-word).

Here is the honest framing. Nobody receiving your caption is auditing the spelling. The reason it is worth getting right is not correctness for its own sake - it is that fussing over the word is the thing that stops people posting at all, and the post was the point.

So: monthsaries. One r. Now go write the caption. And if you are not sure which date you are even counting from - a surprising number of couples are not - our piece on [the best date to celebrate a monthsary](/blog/best-date-to-celebrate-monthsary) sorts that out, and the [days-together calculator](/blog/how-many-days-have-we-been-together-calculator) will tell you exactly how many months you have racked up.