Why are the endings in "я студентка" and "я была студенткой" different?

Question

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)?

Answer 1

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.

Answer 2

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.

Answer 3

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.

Answer 4

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).