Joy of Numbers

Mmm numbers. So there are two angles to today’s post, but both concern numbers. Firstly take a gander at the numbers 1 to 10:

  1. unu
  2. du
  3. tri
  4. kvar
  5. kvin
  6. ses
  7. sep
  8. ok
  9. naŭ
  10. dek
The first angle falls under the “alluring words” category. I think they are so simple and cute. They seem like the bare minimum, and yet still smack of what makes me think “three” or “nine” or “eight” from the various languages I’ve looked at. This is exactly what numbers should be: not cumbersome.

Next, for what’s interesting. I think the Esperanto number system is very nicely laid out (in terms of making the numbers greater than ten), but that’s a story for another day. Today I’m marvelling at the ease with which one can construct the different types of number. I’ll explain.

The above numbers are “cardinal” numbers, the numbers we use to count things, to state how many things  there are:

  • Estas du kameloj = There are two camels
  • Estas kvar viroj = There are four men
In order to make the “ordinal” numbers (the numbers we use to order things in a list e.g. first, second, third, fourth…), we simply add “a” :
  • First = unua
  • Second = dua
  • Third = tria
  • Fourth = kvara
  • Fifth = kvina
You can also change these to other parts of speech like “unue” or “trie” = “firstly” or “thirdly” respectively.

In order to make multiples, we simply use “-obl-“. Then the correct part of speech ending. So, the multiple made from “two” is “double”. If used like an adjective in “double shot” we use “duobla” (“a” the adjective ending). If we use like an verb “The slime doubled in size” we would use “duoblis” (“is” the past tense verb ending).

  • Single = unuobla
  • Double = duobla
  • Triple = triobla
  • Quadruple = kvarobla
Note that you can easily use these endings on ANY number, unlike English where I start to not be able to think of what comes next…

In order to make fractions, we use the “-on-” suffix. Specifically, this makes the reciprocal of a number. So if you add it to 4, you get 1/4 (quarter), if you add it to 8 you get 1/8 (eighth).

  • (A) half = duono
  • (A) third = triono
  • (A) quarter = kvarono
In order to make repetitions, we use the root “foj” = “time,occasion”. Remember from the word “iufoje” = “sometimes”?
  • Once = unufoje
  • Twice = dufoje
  • Thrice = trifoje
And you can keep going: kvarfoje, kvinfoje… I have no idea if we have English equivalents, other than just saying “four times”, “five times”.

In order to make groups, we can play with the suffix “-op-“. Again, depending on the part of speech ending, we can get interesting different effects:

  • du = two
  • duopo = a group of two, duet
  • duopa = is an adjective that describes something that is made up of two members
  • duope = by/in (groups of) twos
Look at all the different English changes you have to learn for just a few (a,op,obl,foj etc.) simple Esperanto ones! And you can’t even reliably permute all different types of number with English! Esperanto saves us again.

11 thoughts on “Joy of Numbers

  1. Oops, WordPress didn’t like my angle brackets, let’s try that again…

    ‘If we use like an verb “The slime doubled in size” we would use “duoblis”’ — actually, the verb there would be “duoblighi”, that is, to become /duobla/; “duobli” means to *be* double.

    Incidentally, have you run across the Tekstaro yet? It’s a wonderful searchable corpus of Esperanto, at:

    I was just using it to double-check my statements above. Apparently no-one’s ever even used the verb “duobli” before! 🙂


    • I am reading the blog backwards (let me first congratulate Andy for this excellent work) and again I come across to something which I do not understand in E-o.

      I know there are “Transitivaj” (tr) and “Netransitivaj” (ntr) verbs. I know that tr verbs have “objektoj” whereas ntr verbs don’t have because they are verb forms.that affect the “subjekto” and not an “objekto” like the tr verbs.

      NOW, I am thinking that
      1) if a verb is tr it should also have the -iĝ (ntr) form which will make the action return to the subject.
      2) On the other hand if a verb is ntr it should also have the -ig (tr) form so that it can direct the action to an “objekto”.

      Funny enough to know there are verb forms like :
      fari – farigi – fariĝi (
      n/a – duobligi – duobliĝi (

      Yet at vortaro ( I can find only the following forms (which makes better sense to me) :
      fari – n/a- fariĝi
      duobli – duobligi – n/a

      That’s something which I do not understand, and thus I use those verbs incorrectly.


      • Thank you!

        I’m not entirely sure what the question is, are you just having trouble understanding the interactions between roots and “-iĝ” and “-ig”?

        If so, try not to think of it as “transitive can have “iĝ”, intransitive can have “ig”, but sometimes… etc.”. Think of it more like:

        “-iĝ” means “to become [root]”. So “duobliĝi” makes perfect sense, because it just means “to become double”.

        “-ig” means “to cause [root]”. So “farigi” also makes perfect sense, because it just means “to cause (someone/something) to do/make”.

        Remember that no dictionary will ever be able to cover all the possibilities of word building in Esperanto. So just because a compound doesn’t appear in one, doesn’t necessarily mean that it doesn’t make sense. So long as the meaning can be logically determined from its components, you’re fine! 🙂


        • Thanks for the answer. The question here was that I do not understand how it is possible to have all three forms of a verb. Some examples :

          1) fari – farigi – fariĝi (
          2) naski – naskigi – naskiĝi (

          Maybe there are trivial differences that I do not grasp. For example between fari and farigi or between naski and naskigi.

          Also why we do not have the form “duobli” but we have “duobligi” instead :

          3) n/a – duobligi – duobliĝi (

          and why at different places the forms are not consistent, for example at lernu we just have :

          4) fari – n/a- fariĝi
          5) duobli – duobligi – n/a

          Well, you answered this to some extent. You see, I am always trying to figure out some symmetries so as not to bother which verbs are used at which forms 🙂 Yet I think there are not clear cut answers. I should go and explore PMEG again. Thanks.


        • You are right, there is certainly not a clear cut answer. Once you learn the meanings of the suffixes (including “-i”), then all words are permitted that you can make logical sense out of.

          For example, with “duobl-” which acts kinda like a quality root, adding “-i” does what it does to any quality root, which is “to be [quality]”:

          duobla = double; duobli = to be double
          bela = beautiful; beli = to be beautiful

          So long as you can think of a logical meaning for it, you can add any suffix:

          duobliĝi = to become double
          duobligi = to double (to make double)

          Just because a particular compound word isn’t listed in the dictionary, doesn’t mean it can’t be used. So there is no “we do not have this form”, because you just made that form! 🙂


  2. ‘If we use like an verb “The slime doubled in size” we would use “duoblis”’ — actually, the verb there would be “duoblighi”, that is, to become /duobla/; “duobli” means to *be* double.

    Incidentally, have you run across the Tekstaro? It’s a wonderful searchable corpus of Esperanto, at . I was just using it to double-check my statements above. Apparently no-one’s ever even used the verb “duobli” before! 🙂


  3. How about twin(s) triplet(s) etc… Would you use -op-?
    Would it be like…
    ŝi estas duopo — she is a twin.
    La duopa turoj — the twin towers.



    • Hmm. It feels like there should be a way of grouping them, right?

      Though “ŝi estas duopo”, says that “she is a group of two”. When what you want to say is that she’s one of a group. So maybe insert “(unu) de” before “duopo”. But still, this is very generic, and does just mean duet, or group of two (alternatively, it might be possible to use “duopano”, the suffix “an” means “member of “). Perhaps if you were already talking about offspring and birth, then yes, maybe in this context “de duopo” can be interpreted as “of/from twins”.

      But if you didn’t have that context, or it was ambiguous in other ways, there is an alternative. What we’re actually missing here, is some notion of birth, or offspring, because without it, its just a grouping of some kind. One other thing to note before the explanation, is that “duo” could be considered a more general term for “duopo”, because not only can it mean a group of two, but also “the number two” (since it’s just the noun form of “du”). For this reason (and the convenience of the shorter word), the shorter form is often used in word building.

      So given the word “naskito” which means like “new-born” or “one having been born”, from the verb “naski” , “to give birth to”, we now have a concept of being born. So taking “duo”, we slap it together with “naskito”, to get “dunaskito” = “a twin (born in a two)”. Could conceivably leave the “o” after “du” but not necessary (though remember there is another word for twin: ĝemelo). Now you can have: trinasktio, kvarnaskito…

      “La duopa turoj” seems much closer to the mark (though “duopaj” is needed for plural agreement). But it’s more like “the paired towers”. I’d first capitalise the words to show you are speaking of a particular entity, then people will be less likely to think you are talking about any old pair of towers.

      But the problem is, “twin” carries a mean of “being the same” that “op” just doesn’t cover. “op” only says that the entities belong in a group, not that they are all identical in the group. But now we’ve established a way of representing “twin”, we could go:

      “La dunaskitaj/ĝemelaj turoj” = “the twin towers”, describes a pair of towers that are twinned in some way.

      But possibly better:

      “La Dunaskitturoj” = The Twin Towers, says that it’s a particular two towers that are known or generally described as being twin towers. (Alternatively “La Ĝemelturoj”, which happens to be the way that the Esperanto wikipedia uses to describe them).

      Hope those ramblings make sense!


    • In the third long paragraph I mean “trinaskito”.

      If you are concerned as to why “duo” or “trio” might be a more general version of “duopo” or “triopo” (as mentioned below). Then consider English usage:

      I can say “They arrived in a three” (trio) rather than “They arrived in a group of three” (triopo). Alternatively, check out the PMEG page about this:


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