In the following sentence:

Не нужно объяснять, чем так хороша физическая активность зимой.

I didn't understand what this чем meant, so I tried using Google Translate to get the feel of the structure.

No need to explain why physical activity in winter is so good.

It seems to mean an interrogative pronoun, but in my dictionary, there is no such usage. It only lists чем for comparison.

Another use of чем is as an instrumental case, but объяснять seems to take an object as an accusative, so it should be что, not чем, I think.

So I think I'm missing something. How does чем work here? Can I use it like почему?


3 Answers 3


The instrumental is actually an object of хоро́ш. The adjective хоро́ш can take an object to say why something is good:

  • Э́тот ме́тод хоро́ш свое́й простото́й. - This method is good for its simplicity.
  • Чем хоро́ш э́тот ме́тод? - Why is this method good?

Quite often the object is a relative clause introduced by тем, что:

  • Кни́га хороша́ тем, что она́ ли́чная, жива́я.
  • Э́тот подхо́д хоро́ш тем, что мо́жно испо́льзовать любо́й компью́тер, подключённый к Интерне́ту.
  • Молоды́е го́ды хороши́ тем, что ты ещё не состоя́лся, но что́-то уже́ зна́ешь и уме́ешь и мно́гое впереди́.

The set expression «хоро́ш собо́й» means 'good-looking':

  • Когда́ я была́ молода́ и хороша́ собо́й, я мно́гое себе́ позволя́ла.
  • В мо́лодости она́ была́ хороша́ роско́шной весе́нней красото́й, а тепе́рь каза́лась хру́пкой.
  • Хорош собой is very interesting! I recently learned that хорошенька means pretty, and not good. Thank you!
    – CocoPop
    Dec 6, 2021 at 20:08
  • 1
    Yes, I've also seen «хорош лицом», although I'd hardly use it myself. Dec 7, 2021 at 10:31
  • 1
    Хоро́шенькая is only used in its full form. And yes, it does mean 'pretty'. Dec 7, 2021 at 10:32

I would translate this sentence as follows:

Не нужно объяснять, чем так хороша физическая активность зимой.

The benefits of exercising in the winter need no explanation / go without explaining / speak for themselves.

Чем, here, basicaly clarifies by virtue of what something or someone is [adjective]. In this example, in what way winter exercise is good; wherein lie its benefits. Key here is the instrumental, which fundamentally delineates by what means an action is carried out, and, as an extension of that function here, in reference to an adjective, it delineates by virtue of what characteristic(s) someone or something personifies or manifests the quality or qualities expressed by said adjective.

  • 1
    красна изба не кутежами, а своевременными коммунальными платежами
    – Quassnoi
    Dec 7, 2021 at 0:36
  • Sorry, I don't understand.
    – CocoPop
    Dec 7, 2021 at 14:31
  • it's a relatively well known pun using this particular construct. I thought it would be funny to post it here, because you had mentioned in another comment that хорош собой was interesting. Can you see the pun, and, if not, are you interested in an explanation?
    – Quassnoi
    Dec 7, 2021 at 14:56
  • I give up!)) Please explain.
    – CocoPop
    Dec 7, 2021 at 17:38
  • There's a proverb не красна изба углами, а красна пирогами, which means "what makes a home nice is not the walls, but the hospitality" (literally, "a log house is good not by virtue of its corners but of its pies"). The pun changes it to "what makes a log house nice is not the booze parties but the utility payments made on time". The mix of styles (dated rural language and concepts on one side, slogans in officialese on another) is what makes it funny to me.
    – Quassnoi
    Dec 7, 2021 at 17:58

You can think of physical activity as having some parts, aspects, factors or features. Some of them may be positive.

So, the phrase literally means "It is not needed to explain with/by what [factors] physical activity is good in winter".

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