"He thinks you know his brother."

Translation: Он думает, ты знаешь его брата.

[mechanarwhal]

Why брата? I thought 'brother' would be in the accusative here?

[apveay]

This masculine noun is animate and ends in a consonant (брат), so in the accusative form, you add “а” in the end.

[mechanarwhal]

Ahh, of course! Thank you!

[mahankr]

As hinted at by apveay, animate masculine nouns have an accusative form that is identical to the genitive form. However, any adjectives that describe them still have their normal accusative form.

[RWang2017]

What is the difference between animate noun and inanimate noun? Could you please provide some examples here?

[hleviathan]

Animate nouns are things that are alive and can move by themselves, e.g. people, animals. Everything else is an inanimate noun, e.g. concepts, plants, cars.

Source: http://www.russianlessons.net/grammar/nouns_accusative.php

[Jared214089]

Manhankr, actually the adjectives for animate masculine nouns also follow an animate adjectival declension which copies the genitive. For example, "Я люблю моего брата."

[cervec]

why was a comma placed here? In english it wouldn't make sense to separate it because it splits the continuation of a thought.

[slycelote]

In Russian, parts of a compound or complex sentence are typically separated by a comma.

[mosfet07]

This sentence is the equivalent of "Он думает, (что) ты знаешь его брата."

The conjunction что (that) which introduces a new dependent clause, must be preceded by a comma.

[Shivaadh]

Would что be mandatory in formal Russian (eg an academic paper)?

[Janek531]

Why is Он думает ты его брата знаешь wrong?? I'm from Poland and in Polish it makes sense, and Polish and Russian grammar is similar, so why is it wrong?

[helenegee]

Can we also say ты знаешь своего брата?

[anton_t13]

That means "Do you know your own brother?"

[helenegee]

Oh, shoot, thanks for correcting me!

[TheFinkie]

Why is it его, and not своего (or something similar)?

[TheFinkie]

Or would that be "your brother"?

[SjLeonardo]

I'm so happy with the fact I instinctively thought of «брата» instead of «брат» here. Seems like the effort is paying off!

[deactivated user]

It is more natural to say он думает, что ты знаешь его брата.

[HendrikGod]

Why is the verb in the subclause at the end?

[Sven125156]

Why not "он думаешь вы знаете его брата?"

[Sven125156]

Or rather "он думает..."

[clintack]

Why is "знаком" wrong here?

[F4yY9kZj]

Evidently 'что', introducing a subordinate clause, can be omitted following 'думать'. Can this be done also with other verbs of "thinking"? How about 'считать', 'верить', 'воображать', 'предполагать', 'допускать', 'сомневаться', etc.? Can it be done with any non-"thinking" verbs?

[Stephen-Ruski]

why do you need он и брата in the sentence

[Stephen-Ruski]

I still don't understand why you need он in this sentence? if you're actually speaking this to someone, then the context speaks for itself. it's totally unnecessary.