Etymology Usage

What do you call a monthly anniversary?

[Note: This post was updated on Oct. 11, 2020.]

Q: Is there a word like “anniversary” for a monthly event? Say, the second monthly whatever of the day I was hired.

A: As a matter of fact, there is. The monthly equivalent of the word “anniversary” is “mensiversary,” a word you can find in at least one standard dictionary.

The British dictionary Macmillan defines “mensiversary” as “a monthly recurring date of a past event, especially one of historical, national, or personal importance; a celebration commemorating such a date.”

So far, Macmillan is the only standard dictionary to recognize the word, though for at least 200 years people have been suggesting “mensiversary” to fill the gap.

Macmillan doesn’t give an etymology for the word. But it was probably formed by analogy with “anniversary,” using “mens-” (from the Latin mensis, for month) in place of “ann-” (from annus, for year).

“Anniversary,” comes from the Latin anniversarius, which means returning yearly. As the Oxford English Dictionary explains, the Latin word is composed of annus (year) plus versus (turned, or a turning) plus the suffix arius (connected with, pertaining to).

In English, the noun “anniversary” refers to the yearly occurrence of the date of a past event—say a wedding or 9/11 or the Apollo 11 landing on the moon.

As for “mensiversary,” it does indeed exist, but not many people would recognize it as the monthly version of “anniversary.” Now that Macmillan has accepted the noun, perhaps other standard dictionaries will too.

“Mensiversary” also shows up in some Internet dictionaries—that is, in collections of words proposed and defined by Internet users. But it doesn’t appear yet in the OED, which is an etymological dictionary based on historical evidence of use.

The earliest reference we’ve found is from a letter written in 1805 by Sir James Mackintosh: “I always observe its mensiversary in my fancy.”

And we found other passing references to the word in books and journals from nearly every decade since then. So evidence of the word is available if the OED wants to make it “official.”

It appears that some adventurous writers in the past thought that they were making the word up.

In his book Prisoner of War: Or, Five Months Among the Yankees (1865), a Confederate rifleman named Anthony M. Keiley recorded this journal entry for July 9, 1864:

“Today is the first mensiversary of my imprisonment. Any super-fastidious reader who objects to my word-coinage, is hereby informed, that he is at perfect liberty to draw his pencil through the obnoxious polysyllable and substitute therefor any word, or form of words, that will better please him, but I hold it, nevertheless, to be a perfectly defensible creation.”

We think it’s defensible too. There are a a few adjectives that mean monthly, but they’re now obsolete and have been dropped from dictionaries.

One such word is “monthish,” which the Oxford English Dictionary defines as meaning “of or relating to a month; monthly.”

Two more are “mensal” and “mensual,” but they’re no longer used to mean monthly, either, probably because “monthly” does the job much better. Besides, most people would probably associate them, and perhaps “mensiversary” too, with “menses” (menstruation), and “menstrual” cycles.

[Note: Since this post was originally published, a few of our readers obliged with their own coinages for a monthly equivalent of an anniversary:  “luniversary,” “monthiversary,” and  “monthaversary.”

Here’s one comment: “For what it’s worth, we very commonly used the term ‘monthiversary’ at the life insurance company where I worked for many years.  In the administration of a policy, many transactions occur on the policy anniversary, and many occur monthly (for example, crediting interest, deducting charges).  Formally, you can refer to ‘the same date each month’ or words to that effect, but internally the common expression in the industry is ‘monthiversary.’ It really serves a need.”]

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