First of all, we must say that the word "каков" is becoming less and less common, so what I will be talking about below is more of a RECOMMENDATION. In some cases, the word "каков" is more preferable, but often in colloquial speech, native speakers ignore these differences.

КАКОЙ is used in questions, when there are suggested options that don't give specific information (like большой/маленький – large/small, высокий/низкий – high/low);

КАКОВ is used in questions, when one needs MORE PRECISE answer.

Please, compare the following examples and note the sentence structure:

— Какова́ высота́ э́той горы́? // What is the height of this mountain?

— Высота́ э́той горы́ составля́ет 2 178 метров. // The height of this mountain is 2,178 meters.

— Кака́я высота́ у э́той горы́? /// What is the height of this mountain?

— Дово́льно больша́я.// Pretty big.

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— Каково тебе было изучать венгерский язык? // What was it like for you to learn Hungarian?

— Поначалу было труднО, но через год я уже довольно хорошо говорил. // At first it was hard, but after a year I spoke quite well.

OR:

— Было интереснО. / It was interesting.

So here we are interested in the person's attitude to the learning process.

And now compare these ones with как-questions and the corresponding answers:

— Как ты изучал венге́рский язык? // How did you learn the Hungarian language?

— Я изучал его в университе́те. // I studied it at the university.

OR

— Я изучал его самостоя́тельно. // I studied it on my own.

OR

— Я изучал его с репети́тором. / I studied it with a tutor.

OR

— Меня научила моя жена́-венге́рка. // My Hungarian wife taught me.

Thus, unlike каково-questions, как-questions implie the way of learning.

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— У тебя новый парень? Расскажи, какой он. // Do you have a new boyfriend? Tell me what he is like. (here the questioner wants to know how would most people see him, and here the questioner would probably here standard superficial characteristics)

— Ну, он мой ровесник, высокий, накачанный, учится на юриста. // Well, he's my age, tall, beefy, studying to be a lawyer.

— У тебя новый парень? Расскажи, каков он. // Do you have a new boyfriend? Tell me what he is like. (the questioner wants to know how exactly you see him, because you know him much better)

— Он такой умный, добрый, ласковый, так мило улыбается…

OR (the same idea, but formulated with the short adjectives):

— Он так умён, добр, ла́сков, так мило улыбается… // He is so smart, kind, affectionate, smiles so sweetly...

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— У него на счета́х миллионы, а он мне даже сто́льник одолжи́ть не захотел. Каков жмот! // He has millions in his accounts, but he didn’t even want to lend me a steward. What a meanie!

Notes:

- "Каков жмот!" sounds more expressive than "Какой жмот!".

- сто́льник = 100 рублей

Я у него только время спросил, а он меня сразу матом послал. Каков грубия́н! // I just asked him for the time, and replied: "F*ck you". What a cad!

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Бла-бла-бла… – таково моё мнение / такое у меня мнение

Бла-бла-бла… – такова моя позиция / такая у меня позиция

Бла-бла-бла… – таковы основные сложности, возникающие при изучении языка суахили.

Бла-бла-бла… – такие сложности возникают при изучении языка суахили.

This is the information I wanted to share with you. If you have any questions, doubts or additions, please write them in the comments.

© Yevgeni Yeliseyev, 2023