Historical Background on Breton

Breton is a language spoken in Brittany, France. It is related to both English and French. Here are some numbers and rules:

Some Background on Breton number system

Unan = 1, daou = 2, tri = 3, pevar = 4,pemp = 5, c'hwec'h = 6, seizh = 7, nav = 9, -zek is teen (like fourteen, fifteen, etc.), ugent = 20, like in French 80 is quatre-vignt (quatre = 4, vignt = 20, 4 x 20 = 80) something in Breton like tri-ugent would be 3 x 20 = 60, 50 in Breton is hanter kant --> hanter = 1/2, kant = 100.

The Question

"Triwec'h" is an irregular number in Breton, like "eleven" or "quinze". It's value is between 10 and 20. I looked at the answer and it says "triwec'h" is 18. My question is ** how ** you would figure out the value of "triwec'h" with only the background provided in this post?

My Progress(not much)

I think an important hint to solving this problem is that c'hwec'h = 6 since they both have c'h. The "tri" in "triwec'h" is probably 3. Maybe we is also 3, and c'h is 2 instead of daou? So like 3 x 3 x 2 =18, but perhaps for c'hwec'h it is simply 2*3 = 6 because there are two c'h so it is redundant? But that seems unlikely because a more efficient system would be to simply do c'hwe for 6.


Sorry if this seems like a lot to read but I'd appreciate if someone could explain how to do this problem. Here is the link to the whole question:https://nacloweb.org/resources/problems/2020/N2020-E.pdf. The problem is #3. Thank you!

  • 3
    And what is your question here? Commented Jul 11, 2022 at 14:36
  • How would you deduce what triwec'h means based on the rules and vocabulary of the Brenton number system? Commented Jul 11, 2022 at 15:10
  • 2
    @MeltedStatementRecognizing I think the body of the question is still unclear. Adding the actual question at the end in bold would make it clearer
    – Tristan
    Commented Jul 11, 2022 at 15:25
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    thanks. That does help. I would also note that the language is Breton, not Brenton
    – Tristan
    Commented Jul 11, 2022 at 15:38
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    Interestingly in the other brythonic languages we have for 'eighteen': Welsh deunaw (2*9) and Cornish etek (< eth-tek, '8+10'). ALL three moder brythonic languages have different forms for '18'.
    – Davius
    Commented Jul 11, 2022 at 18:06

1 Answer 1


The data which is the base for the problem (plus experience with many other languages) tells you that big numbers are often combinations like "five tens" i.e. 5x10. The similarity in form gives you the initial parsing tri+wec'h, which strongly resembles "three sixes" which is 18, fitting the possible range. What has to be explained – ultimately – is the variation in form between wec'h and c'hwec'h.

That is as far as you can reason given the data, which is why the question only asks for a translation. You would have to study the language in greater depth to understand why c'h comes and goes at the beginning of the number. Looking at a popular source for historical linguistics (Wikipedia), you see the reconstruction for "6" in Brythonic as hwex which is quite close to the claimed Breton pronunciation xwɛx. That means then that /x/ deletes in the compound (it isn't added) to the bare noun. You can start reading about Breton mutations, if you want to understand why this happens, but that's way outside the scope of the test.

  • The individual words of the complex numbers provided show only addition and multiplication. Given that the result must be between 10 and 20 and the the first member is likely "tri-," meaning "three," 10 and 20, there remain only a few candidates that can work out mathematically. Lastly, if we know Breton is Celtic, we may be expected know that change in initial consonants is likely. The only possible answer is that "(c'h)wec'h" is the answer. Commented Jul 11, 2022 at 16:14
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    This pseudo-mutation of /x/ is not even regular (and isn’t synchronically a mutation at all since /s/ doesn’t mutate in Breton). Similar irregularities are found in all the Insular Celtic reflexes of *sw, but they’re fairly unpredictable and there aren’t many of them. Commented Jul 11, 2022 at 17:07

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