I am looking for a proper single work term to describe one third of a calendar year. Trimester does not seem correct as it seems to refer to a period of three months (one third of a pregnancy or one third of an academic year).



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    +1 for the find, but if almost nobody knows the word, then almost nobody knows the word. Why use a word that most readers will have to look up in a dictionary to understand? "three months" is pretty succinct :) – e.James Apr 29 '11 at 20:39
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    I had a tertile once we used to feed it flies but it died. The end. – Robusto Apr 29 '11 at 21:10
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    @e.james: Erm... "three months" is pretty succinct, but "four months" is more like a third of a year. Not that I think much of tertile, which is really just a ridiculously uncommon high-falutin alternative to third. Would we seriously want to call a two-month span a sextile? I think not. – FumbleFingers Apr 29 '11 at 21:14
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    @FumbleFingers we use quartile all the time! – corsiKa Apr 29 '11 at 21:25
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    @glowcoder: Trimester certainly does mean three months, from the Latin tres meaning three and menses meaning months. – Henry Apr 29 '11 at 22:17

The term for a four month period is quadrimester. Quad = 4 mense= month

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    You are correct, but it would be good if you backed this up with further references to help people, because it is not a word commonly used in today’s English. It comes from Latin quadrimestris, with the meaning you give it. The French spell it quadrimester as we do, but the Spanish spell this word cuatrimestre in their language, with the d>t change explained by influence of their word for four, cuatro. – tchrist Oct 21 '14 at 0:18
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    The french spell it quadrimestre, not quadrimester. Just like we say trimestre and not trimester – Amandine FAURILLOU Aug 25 '15 at 8:37

There is a difference between a duration period of three months as in "trimester" and an event occurring every 3 months as in "quarterly". In the same vein you would have a quadrimester or tri-annually, both being correct in the right context.


triannually, triannually ,1/3 of the year

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    You've written triannually twice. Could you please provide a quote or a reference to back up your suggestion. – Mari-Lou A May 13 '14 at 6:57

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