The masculine form of "one" is "один," but it is "одна" and "одно" for the feminine and neuter, respectively. Why? In other words, why isn't it "одина" or "одино"?

My inquiry into this has been little more than a Google search, but after attempting various searches and taking a look at several pages to include those from textbooks, I have found nothing that addresses the fact that this word actually drops a letter to form the feminine and neuter forms. If I am not mistaken, this is actually called syncope in linguistics and refers to the loss of medial vowels in a word.

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    Syncope is the right term. It is quite common in Russian, but not usually with "и". It's much more common with "е" and "о". Commented Mar 3, 2021 at 7:44

2 Answers 2


This one is actually non-trivial. As @shabunc mentions, at a certain moment the root (which was originally один-) started to exhibit alternations between и and the ultrashort ь. However, if ь simply won over и, we would have something along the lines "одён - одна - одно" (which Zaliznyak's system in "Russkoe imennoe slovoizmenenie" actually predicts, he needs a special rule to change одён to один when going back from the abstract view ("условный вид")). So the root один was retained in nominative singular (and in some derivatives like одиночный, одинокий) but root одьн was chosen for declension (and for some other derivatives like однажды, однако - notably never in strong position though), leading to an almost unique situation of having a stressed fleeting и (only яиц has the same, but there one can at least point at the neighboring j - which is not quite enough either, compare заём - not *заим).

Also, I need to mention that historical deletion of ь/ъ is not conditioned by stress (see Zaliznyak 1985, ch. 3) but only by segmental context.

  • this is a very nice answer (and I up-voted) but can not help but notice that you rather explain why "один" is "один" ;)
    – shabunc
    Commented Mar 4, 2021 at 23:21

Well, in Old East Slavonic - which is in Russian called more often древнерусский - following forms are attested: одинъ / одьнъ, одина / одьна, одино / одьно. Note that here "ь" is not a soft sign but a ultrashort vowel of course, so called front yer). The 'ь' form is a later development, thus "и" was reduced to 'ь'.

So this forms were exactly like you'd rather expect them to be: logical and predictable ) And from historical standpoint the reduction of "ь"/"ъ" in unstressed positions a very common phonetic process in Russian evolution - there are hundreds, if not thousands examples of such reduction, like правьда -> правда, чьто -> что, кънига -> книга.

However, I honestly think that such questions are better to be asked on https://linguistics.stackexchange.com/ - since this process hadn't happened in modern Russian (which is our main focus) but actually preceded its formation.

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    I like your answer, but, somehow, I Iike the one from Viridianus better. Nevertheless, I see your point about how this might be better for the Linguistics SE. However, since this question was actually asked by someone who did not know much Russian in a Russian class designed for beginners, I think it might be good to just leave it here. Out of respect for you and your logic on this, I will keep questions of this nature to a minimum. Please don't take my resistance to your suggestion as a lack of appreciation for your answer. I enjoyed reading it and consider it good reference for the future.
    – Lisa Beck
    Commented Mar 27, 2021 at 8:53
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    @LisaBeck no worries, feel free to down-vote any answer you don't like, up-vote and accept any answer you like - it's never personal. Also feel free to post any questions you find on-topic, if they are actually not - quite often they can be transferred to different stack or edited.
    – shabunc
    Commented Mar 27, 2021 at 9:19

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