A learner still, I'm looking at numbers. I can relatively easily learn stuff when there's a rule or a pattern, but I'm curious why the numbers in Italian change from :

to dici-xx
at 17?

This is the body of a previously asked question about the same issue (merged with this one):

Let's count in Latin from one to twenty:

ūnus/ūna/ūnum, duo/duae/duo, trēs/tria, quattuor, quīnque, sex, septem, octō, novem, decem,

ūndecim, duodecim, tredecim, quattuordecim, quīndecim, sēdecim, septendecim, duodēvīgintī, ūndēvīgintī, vīgintī

As pointed out by symbiotech, "octodecim" and "novemdecim" were also used in Latin, but they didn't survive. On the other hand, as pointed out by martina, "dĕcem (et) sĕptem" was also a common form for "septemdĕcim".

In Attic Greek it was:

ΕΙΣ/ΜΙΑ/ΕΝ (heis/mia/en), ΔΥΟ (dúō), ΤΡΕΙΣ/ΤΡΙΑ (treis/tria), ΤΕΤΤΑΡΕΣ/ΤΕΤΤΑΡΑ (téttares/téttara), ΠΕΝΤΕ (pénte), ΕΞ (héx), ΕΠΤΑ (heptá), ΟΚΤΩ (oktṓ), ΕΝΝΕΑ (ennéa), ΔΕΚΑ (déka),

ΕΝΔΕΚΑ (héndeka), ΔΩΔΕΚΑ (dódeka), ΤΡΕΙΣΚΑΙΔΕΚΑ (treiskaídeka), ΤΕΤΤΑΡΕΣ ΚΑΙ ΔΕΚΑ (téttares kaì déka), ΠΕΝΤΕΚΑΙΔΕΚΑ (pentekaídeka), ΕΚΚΑΙΔΕΚΑ (hekkaídeka), ΕΠΤΑΚΑΙΔΕΚΑ (heptakaídeka), ΟΚΤΩΚΑΙΔΕΚΑ (oktōkaídeka), ΕΝΝΕΑΚΑΙΔΕΚΑ (enneakaídeka), ΕΙΚΟΣΙ(Ν) (eíkosi(n))

Now let's count in Italian:

uno, due, tre, quattro, cinque, sei, sette, otto, nove, dieci,

undici, dodici, tredici, quattordici, quindici, sedici, diciassette, diciotto, diciannove, venti.

But numbers from eleven to twenty could also have been, just hypothetically of course (adding accents for clarity's sake):

diciùno, diciaddùe, diciattré, diciacquàttro, diciaccìnque, diciassèi, diciassètte, diciòtto, diciannòve, vénti


undici, dodici, tredici, quattordici, quindici, sedici, settèndici, ottòdici, novèndici, venti.

In Spanish it is:

uno, dos, tres, cuatro, cinco, seis, siete, ocho, nueve, diez,

once, doce, trece, catorce, quince, dieciseis, diecisiete, dieciocho, diecinueve, veinte

In Portuguese:

um, dois, três, quarto, cinco, seis, sete, oito, nove, dez,

onze, doze, treze, catorze/quatorze, quinze, dezasseis/dezesseis, dezassete/dezessete, dezoito, dezanove/dezenove, vinte

In French:

un, deux, trois, quatre, cinq, six, sept, huit, neuf, dix,

onze, douze, treize, quatorze, quinze, seize, dix-sept, dix-huit, dix-neuf, vingt

Following martina's hint here are the number words from one to twenty in Romanian:

unu, doi, trei, patru, cinci, şase, şapte, opt, nouă, zece,

unsprezece, doisprezece, treisprezece, paisprezece, cincisprezece, şaisprezece, şaptesprezece, optsprezece, nouăsprezece, douăzeci

I find Latin, Italian, Spanish, Portuguese and French constructions for number words bizarre and inconsistent (whereas in Romanian it seems they are perfectly consistent - thanks martina for her hint - as well as in Ancient Greek). Is there any academic work on the history of number words in Latin/Italian/Spanish/Portuguese/French where the origin of number words from eleven to nineteen is tracked down, documented, explained, discussed?

  • 5
    What about Romanian? Commented Dec 20, 2013 at 11:57
  • 1
    Apparently Romanian number words from 11 to 19 are perfectly consistent! And yes, I think that would deserve a separate explanation because it would only be reasonable to expect from Romanian number words the same inconsistencies of Latin, Italian, Spanish, Portuguese and French.
    – user193
    Commented Dec 20, 2013 at 12:00
  • 2
    Is this question on topic? It's probably much more suited to Linguistics...
    – Sklivvz
    Commented Dec 27, 2013 at 10:31
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    Welcome on ItalianSE!
    – abarisone
    Commented Jul 3, 2018 at 5:37
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    @Charo It is indeed a duplicate, but I don't think the answers there are really good enough. I vaguely remember seeing a similar question on linguistic.SE with a better answer, I'll see if I can dig it out. In the meantime I suggest we leave this question open.
    – Denis Nardin
    Commented Jul 3, 2018 at 10:19

3 Answers 3


An interesting explanation is given in the article "L'etimologia: implicazioni cognitive ed evidenze testuali (a proposito di bonus, malus e del "vaso dell'artefice capace")" by the linguist Domenico Silvestri, published in Linguistica Zero, Rivista del Dottorato in Teoria delle lingue e del linguaggio dell'Università degli studi di Napoli "L'Orientale" and in the book Etimologia fra testi e culture (edited by Giulio Paulis e Immacolata Pinto from Università di Cagliari). According to the author the origin could be the diffusion of the quaternary numeral system. Being sixteen equal to four times four it assume a particular relevance as marking the start of a new sequence.

Here is an excerpt from this article. You can find the complete article here.

      Qui accennerò ad alcune ricognizioni pragmalinguistiche, nell'ambito del computo con le dita e sulle (fra le?) dita, tra mondo indoeuropeo e dintorni. Tutto dipende in effetti e in prima istanza dal computo manuale nelle sue manifestazioni più antiche (e più imprevedibili). In questa sede mi limiterò a qualche esempio partendo da dati linguistici più vicini: nella serie italiana dei numerali cardinali da 11 (undici) a 19 (diciannove) colpisce, dopo 16 (sedici), l'inversione dell'ordine reciproco di unità e diecina: abbiamo 17 (diciassette), 18 (diciotto), 19 (diciannove), mentre prima avevamo 11 (undici), 12 (dodici), 13 (tredici), 14 (quattordici), 15 (quindici), 16 (sedici). Alla fissità più che comprensibile della "rappresentazione grafica" per cifre non corrisponde in tutti i casi qui visti la configurazione sequenziale degli elementi linguistici. Il fenomeno, che non ha fondamento etimologico nella seriazione dei numerali cardinali latini, ricompare in francese (seize "16" vs dix-sept "17", dix-huit "18", dix-neuf "19") e in spagnolo (con un'anticipazione dell'inversione a quota "16" , che è dieciseis), mentre è del tutto assente in inglese e in tedesco e in altre lingue. Qual è la spiegazione? Propongo di cercarla in una circostanza di ordine generale, cioè la grande diffusione in moltissime lingue del mondo della numerazione a base "4", che è sempre – dove è possibile l’espressione della marca del numero – un plurale perché si riferisce al massimo del computo fatto con il pollice sulle dita o fra le dita. In latino, greco e sanscrito il numerale "8" è espresso pertanto alla forma duale (sc. "8" come doppio o, meglio, come coppia di "4", che è il numero massimo della prima seriazione di computo) e rappresenta pertanto un'antica parola per "quattro", che per una felice circostanza emerge pure in due tradizioni linguistiche non indeuropee (berbero okat "4", georgiano otxi "4" con normale metatesi della sequenza consonantica). Se “quattro” è così rilevante nella numerazione arcaica fatta sulle dita di una mano (non si dimentichi che il pollice non è dito contato ma dito contatore e se è aggiunto nel computo ecco “cinque” con l'enclisi conclusiva del –que come mostrano le forme latine, greche e anticoindiane!), non sorprenderà ora il fatto che "16" sia considerato un ulteriore massimo di una prima serie di computi (“4” volte "4"!), per cui nello spagnolo l'inversione marca il "completamento" una prima serie di computi, in italiano e in francese invece l'inizio di una seconda serie di computi. A riprova di quanto affermo faccio notare che in latino novem “9”, che ha una indubbia connessione etimologica con la nozione di "nuovo" (cfr. lat. novus, –a, –um), diventa a questo punto eloquente testimonianza del fatto che dopo il computo di una doppia quartina (lat. octō è un duale!) si conti di nuovo (novem appunto).

  • 1
    Welcome to Italian.SE!
    – Charo
    Commented Aug 23, 2018 at 16:19
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    I took the liberty of adding an excerpt from the article to your answer.
    – Charo
    Commented Aug 23, 2018 at 16:45

I found a similar question, where this is suggested by user CapnPrep as a possible answer:

Octodecim and novendecim/novemdecim do exist, although they are not the preferred forms in Classical Latin. I think the explanation is the same as why one might prefer to say "ten to six, quarter to six" instead of "five fifty, three quarters after five". Or if you're 19 years old,you might prefer to say "I'm almost 20" instead of "I'm in my teens". When you get close to the next round number, it is natural to use it as the new reference point, in anticipation.

My only addition to his answer, since in Latin this happens only with 18, 19 numbers, is that it can be related to the age of maturation, the age when a young man was enrolled in the army. In the days before Augustus this was 16 years, but after his rule the age of enrollment was increased to 18. So maybe this way of mentioning 18 as "20 without 2" was some sort of suggestion "that you are mature enough now", "you are considered a man" etc.

  • As it does not report any source, I am not really convinced by this answer. However the more I read it the more I think that it is an interesting hint anyway, and it has been the only one also, that's why I have "accepted" it.
    – user193
    Commented Feb 19, 2014 at 21:04
  • I don't think this answer is credible.
    – Charo
    Commented Aug 23, 2018 at 20:08
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    I've downvoted this answer because it comes from a source (an Internet forum) which has no credibility at all. Please have a look to a newer answer which comes from an article by a professor in linguistics on a specialised university publication.
    – Charo
    Commented Aug 26, 2018 at 16:02

My guess here is simple: the more a word is used in commmon parlance, the more it can violate rules--look at the conjugations for "be" and "go"--a less common verb couldn't support irregularity. "Thrive" may not be common enough to support the irregular past participle "thriven".
The rules for numbers 20-29, 30-39, etc., all have the formation of the first digit (venti/trenta/etc) and then the second digit. While the teens in Latin were consistent as a set, they were irregular with respect to other large numbers.

11 and 12 are common enough to support irregularity in any language.

For 15 and 14, they were common enough to support irregularity in Spain and Italy, but higher sums didn't have enough commonality, so people fell-back to the rule for most large numbers: first digit first, second digit second.

There is no hard-and-fast rule to determne when a word goes under the commonality threshold, so it might be different in different regions.

  • 2
    Don't forget to say that digits didn't exist in writing in Europe until the 10th century. And let's not make anyone believe that "first digit first, second digit second" is a general rule. In German it's the other way round, for example, and in French, contrary to what you would suppose, things get quite a bit complicated between 70 and 99. Commented Aug 16, 2015 at 20:54

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