Чёрная ворона сидит у окна.

Because ворона is a feminine singular noun, and the adjective has to agree with it.

• чёрный = masculine
• чёрная = feminine
• чёрное = neuter
• чёрные = plural

So:

• чёрная ворона = black crow

Russian adjectives change their endings to match the noun’s gender, number, and case.

In Russian, many nouns ending in -а or -я are feminine. Ворона ends in -а, so it is feminine.

That is why:

• the adjective is чёрная
• the verb is сидит in 3rd person singular, which works for any singular subject, including feminine ones

A useful comparison:

• чёрный кот = black male cat
• чёрная ворона = black crow

Because after у, Russian normally uses the genitive case.

The base form is:

• окно = window

But after у:

• у окна = by the window / near the window

So окна here is the genitive singular form of окно.

Here у means by, near, or next to.

So:

• у окна = by the window / near the window

It does not literally mean at in every context, and it does not mean the crow is necessarily on the window. It just tells you the crow is positioned close to it.

Сидит is the 3rd person singular form of сидеть (to sit).

The subject is ворона = the crow, which is singular, so the verb must also be singular:

• я сижу = I sit / am sitting
• ты сидишь = you sit / are sitting
• он / она сидит = he / she sits / is sitting
• они сидят = they sit / are sitting

Since there is only one crow, Russian uses сидит, not сидят.

It can mean either, depending on context.

Russian present tense often covers both:

• is sitting (right now)
• sits (generally / habitually)

So Чёрная ворона сидит у окна could mean:

• A black crow is sitting by the window
• A black crow sits by the window

Usually the situation tells you which one is meant.

Russian has no articles.

So ворона can mean:

• a crow
• the crow

And окна can mean:

• a window
• the window

The exact meaning depends on context. This is very normal in Russian.

Yes. Russian word order is more flexible than English because the endings show the grammatical roles.

The neutral order here is:

• Чёрная ворона сидит у окна.

But you could also say:

• У окна сидит чёрная ворона.
• Сидит чёрная ворона у окна.

These versions are all grammatical, but the emphasis changes:

• starting with у окна puts more focus on the location
• starting with сидит can sound more descriptive or narrative

Чёрная is pronounced roughly like CHYOR-na-ya.

Important points:

• ё is always stressed: чёр-
• ч sounds like ch in check
• ё sounds like yo
• the ending -ая in careful speech is -aya, though in natural speech it may sound a bit reduced

Also, in printed Russian, the dots on ё are sometimes omitted, so you may see Черная. But the correct pronunciation here is still чёрная, not черная with plain е.

Because ворона is the subject of the sentence, so it stays in the nominative case, which is the dictionary form.

• ворона = nominative singular

But окно comes after the preposition у, and у requires the genitive case:

• окно → окна

So the structure is:

• Чёрная ворона = subject, nominative
• у окна = prepositional phrase with genitive

Not usually. У окна means by the window, near the window, or next to the window.

If you want to say on the window or on the windowsill, Russian would normally use different wording, for example:

• на окне = on the window / on the windowsill (depending on context)

So у окна is about proximity, not being physically on top of it.