I saw a new comic on xkcd http://xkcd.com/1602/ and understand that I don't get to go to the linguistics club.

Megan talks to Ponytail. Megan: You should come to our Linguistics Club's sesquiannual meeting. Megan: Membership is open to anyone who can figure out how often we meet.

I Googled the word 'sesquiannual' and some say that it means it 'happens every one and a half years' - every 18 months, and some say it means it 'happens one and a half times a year' - every 8 months. So I need help.

  • 5
    Now that meeting will be overcrowed. And they need to change schedule to sesquiennial to accomodate everyone.
    – Chieron
    Nov 12, 2015 at 11:49
  • 1
    @Chieron - Only if you know for sure the exact date of one of the meetings. Knowing how often they meet is useless if you don't have a point of origin to start from... Nov 12, 2015 at 16:13
  • @DarrelHoffman to have half a meeting it must run from NYE to NY every other year so for any given year you know they must meet on one of 2 specific days.
    – JamesRyan
    Nov 13, 2015 at 16:50

3 Answers 3


http://www.explainxkcd.com/wiki/index.php/1602:_Linguistics_Club explains:

A SESQUIANNUAL meeting is one that occurs one and a half times every year; equivalently, 3 times every 2 years, or once every 8 months. It comes from the Latin prefix "sesqui-", which means "one and a half times", and "annual", which means "happening once every year".

This is NOT to be confused with SESQUIENNIAL, which means every one and a half years, or 18 months. A linguist or Latin scholar, the joke suggests, should be able to figure sesquiannual out as "half-and-one every year".

This is an extension of the common confusion between "biannual," meaning "twice a year", and "biennial", meaning "once every two years". Compare with the Sesquicentennial Exposition celebrating the first 1½ centuries of the United States.

  • 8
    I never knew that about -annual and -ennial. This naturally leads to a second question, is there a similar change that takes place for other range periods like bi-monthly or bi-weekly? Nov 12, 2015 at 16:31
  • 6
    The terms bi-monthly and bi-weekly are always confusing,unfortunately. Nov 12, 2015 at 17:13
  • 1
    @AndrewLott we have fortnightly for the week-tier, I'm not sure what we have for the month-tier.
    – Flaw
    Nov 12, 2015 at 17:15
  • 3
    A fortnight is a British term, often not even understood by Americans. Nov 12, 2015 at 17:18
  • 6
    Americans understand fortnightly, but it sounds literary, and I don't think it comes naturally to most of us in conversation. I myself use twice-weekly, twice-monthly or semi-monthly, and semi-annually instead of biweekly, etc. For terms of multiple weeks or months I have to resort to longer wording to avoid ambiguity: meetings are held in alternating months or meetings are held every other week or meetings are held every six weeks and so on.
    – choster
    Nov 12, 2015 at 18:59

'Sesqui' means "one and a half" and 'annual' means "yearly".  But if the meeting is held (on average) every eight months, then there will be TWO meetings every second year — which flies in the face of the definition of 'sesquiannual'.

So you must hold 1 meeting and half of another meeting in a given calendar year.... and the only way to do that is, at the second meeting, go through approximately half of the order of business and then call to adjourn.  Reconvene the following year and complete the meeting from the point of adjournment.

  • 5
    Or you could hold one regular meeting and one meeting that doubles as a New Year's Eve party that, of course, runs past midnight of New Year's Day. So 2015-04-01, 2015-12-31 running into 2016-01-01, 2016-08-01, 2017-04-01, etc.
    – shoover
    Nov 12, 2015 at 16:55

Neither sesquiannual nor sesquiennial are in my Shorter OED. "sesqui" is a term which roughly means the ratio of (n+1)/n for some integer n, and is usually associated with 2 (in chemistry it means 3:2 ). 3:2 is the most common meaning, but not the only one; 9:8 occurs in music... I wonder if Monroe meant the double entendre, that it is precisely the people interested in linguistics who would argue over its definition...Somehow, I doubt it...hence a joke a miss.


You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .