My question is this: How did the Russian language end up having different endings in the phrases shown in the title of this post?

Now I will make some remarks to explain precisely what makes me puzzled.

I did some research and found that the form я студентка evolved from the form я/азъ есмь студентка, where есмь is the present tense first person singular form of быть and is no longer used in the Russian language (Source), so есмь is simply omitted nowadays.

Still, whilst была is followed by an object in the instrumental case, есмь is followed by an object in the nominative case, as can be seen in the following illustrative example below:

Азъ есмь Богъ, въ вѣкахъ предсказанный (Source)

Азъ есмь Софья. (Source)

и рече Игорь ко Асколду: «вы нѣста князя, ни роду княжа, нь азъ есмь князь, и мнѣ достоить княжити». (Source)

This means that even before есмь disappeared, it required a grammatical case different from the one required by был, despite есмь and был being one and the same verb taken in the present and past tenses, respectively.

Google shows that people also say я была студентка, but this variant is ~300 times less common than я была студенткой.

I wonder how one and the same verb быть can require one case in the present tense and a different case in the past tense.

P.S. Perhaps it is better to ask the question as follows: Why do people say кем он был, but never say кем он есть and prefer кто он есть (такой)?

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    Я была студентка is used (as you see from Google), but will be perceived as just slightly more formal, more literary... – alexsms May 22 '19 at 7:57
  • Great question, and good answer! – Arioch May 22 '19 at 9:43
  • Look at this my answer: russian.stackexchange.com/a/13104/194 – Anixx Jul 19 '19 at 11:48

To summarize: In the sentence Я студентка. you have студентка (nominative) serving as a predicate without a copula. In the modern usage, the copula is usually omitted in the present tense. If you don't have a copula, your predicate is always in a nominative case. In the sentence Я была студенткой. you have a compound predicate была студенткой (in instrumental form). Generally, both nominative and instrumental cases could be possible with a copula in the past or future tenses.

To analyse in detail, this source claims, that nowadays for the past tense you can actually decline the predicate noun in either nominative or instrumental case. An exception is when a present tense is used (either with or without a copula быть), where a nominative case is compulsory. For the past tense the preference would still tend to be the instrumental case (Я была студенткой.). The first (p. 21) and the second (p. 34) sources confirm that fact: Он был русский. Он был русским., however in negation, an instrumental case (Он не был русским.) is preferable.

While the authors do give preference to the instrumental case, they claim that nominative still plays a role (in some situations), e.g., when a speaker considers predicative as a determinative trait of a subject. Some examples: Он был художник. Он был настоящий художник - you want to really emphasize He was an ARTIST., or Он был американец. Он был талантливый человек. Он был энтузиаст. For more examples, check source 1, p. 23.

In terms of historical development, the choice between nominative and instrumental cases depends on the period. The first source on p. 18 and the second source on p. 26 both claim that until the 15th century, the nominative case was the most commonly used, whereas the instrumental case was only used for indications of professions and ranks. The semantic difference was that the nominative case indicated some permanent state of a subject, whereas instrumental indicated a temporary state. Starting from the 18th century, the instrumental case starts being used more and more often instead of the nominative (again, the exception, as you already pointed out, is in the present tense with or without copula быть, where nominative is used). The semantic difference blurs out with the instrumental case being used within contexts where it wasn't used before. A very detailed analysis is given in the second source on pages 34-37.

  • I wonder if быть+instrumental borrowed the pattern from "стать кем-либо" – Arioch May 22 '19 at 9:45
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    Darya, thank you so much, this is really an enlightening answer! I was unaware of this semantic difference and am now glad that I have learned it. – Mitsuko May 22 '19 at 13:06
  • >>An exception is when a present tense is used (either with or without a copula быть), where a nominative case is compulsory<< I do not yet understand the logic or reason of this exception. The Russians often say кто он есть такой and never say кем он есть таким, but can easily say кем он был, albeit without таким. What adds to the mystery is that in Czech you can use both nominative and instrumental cases in the phrase "I am a student": Jsem studentka and jsem studentkou. Why can't the Russians do what the Czechs can? – Mitsuko May 22 '19 at 13:06
  • @ Arioch, стать is considered as a semi-auxiliary verb. If you open the 2nd source (moderna.uu.se/digitalAssets/122/…) on p. 52, indeed it claims that instrumental has been used with such types of verbs since earlier times of russian language developement. Deeper analysis with a verb стать is given on p. 58. On p. 35 authors say that if you can substitute a verb быть with a verb стать in your sentence, then instrumental case could/should be used. – Darya Shcherbakova May 23 '19 at 1:40
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    @Mitsuko, I don't know if you are just learning Russian for fun or trying to analyse its development from a historical POV. While Russian and Czech do have the same Slavic roots, its development wasn't really in parallel, influenced by a lot of history in between, they belong to different East and West Slavic groups. It's interesting to analyze when the split has happened and why, but it would require a lot of digging into (check en.wikipedia.org/wiki/Slavic_languages as a start). If it's not your goal, sometimes you just need to accept that it is the way it is and go along with it. – Darya Shcherbakova May 23 '19 at 1:50

I'd rather ask why those ending should match. But wait, they do.

The phrase "Я - студентка" (notice the hyphen, it is commonly* required) is a shortcut for: "Я являюсь студенткой". The shortcut would sound weird if the object preserved the form ("Я - студенткой"); thus it switches to "infinitive" neutral form. The hyphen would signal the verb omission.

The past tense simply doesn't have such shortcut.

The phrase "Я была студентка" is unconventially drammatic (poetic); it is somewhat akin to subject-verb inversion in the English ("The pain felt he").

You should set your mind about nouns and adjectives to always be in a specific form, unless being the subject. "Студентка" is not the subject in your question.

*hyphen is required in similar cases more often than not; however in this particular case a personal pro-noun Я is used together with a noun as the predicate, thus the hyphen should be omitted. Consider these examples: "Моя сестра - студентка", "Моя сестра является студенткой", "Моя сестра была студенткой".

Why do people say кем он был, but never say кем он есть and prefer кто он есть (такой)?

"Кем он есть" is a grammarly forbidden sentence. One can say "Кем он является (сегодня)", if you want to use кем, or "кто он есть" (which you already mentioned).

For the past case one can say either "кем он был" or "кто он был".

If there is some bias towards "кем" in usage frequency between those sentences, it is not rational but rather a matter of preferences.


The use of both Nominative and Instrumental for the past tense is grammatical. They have some different meanings though.

When you use Nominative, you mean exactly what you say: you was that thing.

If you use Instrumental, this can mean you was that thing but also you played a role of that thing or pretended being that thing.

For instance:

Когда я вчера спала я была студенткой = In her sleeping dream yesterday she was a student.

Когда я вчера спала я была студентка = It seems she was fired from her university overnight or maybe she graduated yesterday.

На прошлогодней вечеринке я была школьницей = At the yesteryear's party she was dressed like a schoolgirl

На прошлогодней вечеринке я была школьница = She was a real schoolgirl when the last year's party was going (maybe that's why she did not drink or fuck that time but now she can).

In all cases when you use Nominative you can also use Instrumental, but not vice versa.


Here's couple different questions.

  1. 'я была студентка' and 'я была студенткой' are both correct. The actual difference is regional. Most Russian regions use the first, a couple regions use the second.

  2. The sentence is 'Person был Role'. It actually is a Partitive case. This case nowadays practically absent in Russian, and replaced by Genetive or Nominative (see p.1).

  • объясни чем отличается Partitive от Genetive or Nominative – OmarL May 23 '19 at 11:18
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    en.wikipedia.org/wiki/Partitive_case en.wikipedia.org/wiki/Partitive Партив обозначает принадлежность объекта к группе, а генетив (родительный падеж) обозначает одностороннюю связь между объектом и субъектом. Несмотря на относительную внешнюю схожесть, на самом деле разница в том, что субъект в генетиве может играть роль объекта в другом предложении. А вот группа для партива - нет. Группа всегда будет группой и никогда не станет объектом. – Andrey Chistyakov May 23 '19 at 11:37
  • спасибо болшое. – OmarL May 23 '19 at 11:40
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    Unlikely. Russian does exhibit Partitive (cf. литр чаю/чая to у чая/*чаю), but it never appears in predicative contexts. – Viridianus May 26 '19 at 17:05

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