What I said in the title above seems to be roughly true in the European languages that I have checked, so my question is: Could ancient Indo-European, or a precursor of it, used a suffix that meant "add one" after the root words for 2, 4 and 6 to denote 3, 5, and 7 respectively? I mean, maybe three was "two and one more", five was "four and one more", seven was "six and one more". This could explain the similarity in initial letters for these numbers. Thanks.


3 Answers 3


These words show no signs of sharing a common suffix, let alone one that we can identify as meaning "add one." Actually, there is another explanation often used for this kind of thing: sound changes by analogy that cause counting numbers next to each other to change their first sound to be more similar. This is thought to be the reason why "four" starts with "f" in Germanic languages. (discussed in Historical and Comparative Linguistics, by Raimo Anttila)

Apparently, some think this may also be the source of "s" in the "six" word: the reflexes in Indo-European languages point variously to original *w (Armenian), *sw (Celtic), or *s (Italic, Germanic); one idea is that it started out with *w, and then later an "s" was added at the start by analogy with the "seven" word, and the cluster *sw was then simplified to just *s in some branches. (discussed in the "Italic" chapter, by Robert Coleman, of Indo-European Numerals, edited by Jadranka Gvozdanovic) However, another etymology of Armenian վեց vec' derives it from the cluster *sw via an intermediate step *hw. ("Indo-European 'Six'" by Václav Blažek) The internal structure of the PIE word and the history of how it came to mean "six" are also unclear.

But "two" and "three" are just coincidence as far as I know. In fact, "two" and "three" only start with the same letter in English by coincidence; the sound is not the same, and in other Indo-European languages like German or Spanish the spelling reflects this more: (zwei, drei and dos, tres).

  • Thanks, that is helpful. But concerning your by the way, I meant they were "nearly" the same letter/sound, although not the same, that's why I said "roughly true" instead of "true." Jan 29, 2016 at 3:11
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    @RichardPeterson How are /t/ and /θ/ nearly the same sound? I think that's just an impression amongst English speakers that comes from their both using <t> in English writing. Jan 29, 2016 at 5:16
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    +1. In the Slavic languages, the word for 9 is devet, although *nevet would be expected etymologically (EN. nine, LAT. novem, WELSH naw, etc.). It is the analogy with deset, 10, that accounts for the n > d change in the Proto-Slavic language.
    – Yellow Sky
    Jan 29, 2016 at 13:27
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    And in Russian, 7 and 8 are sem' and vosem', which look/sound parallel, but have clearly been affected by each other (cf Serbian sedam, osam).
    – Colin Fine
    Jan 29, 2016 at 19:18
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    The similarity of 6 and 7 is also found in Semitic languages (eg Hebrew shisha, shav'a), which has led many people (eg Theo Vennemann) to speculate that these are old borrowings into IE from Semitic. However, Welch chwech and saith do not share an initial consonant, and this is generally reckoned to indicate that in IE they had different initials, sw- and s-, which fell together in all the other branches.
    – Colin Fine
    Jan 29, 2016 at 19:22


du̯oe̯ = two

trei̯es = three

q̆etu̯ores = four (derived from q̆et- "fit together")

penq̆e - five

su̯ecstis = six

septm = seven

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    Isn't the PIE "six" word thought to have had a consonant cluster sw, as Colin Fine says? (Also, should that c be k?) Jan 31, 2016 at 19:21

Urdu/Hindi/Hindustani have no such pairings: Aik Du Teen Char Panch Chay Sath Aath Nau Dass

English names of these numbers just happen to have same starting alphabet but the pronunciation is clearly different.

P.S: Sorry would have posted this as a comment but cant do so at the moment.

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