Learn Hardcore Russian: Девушка читает книгу в парке.

The accusative case is used for the direct object of the verb – the thing that is being acted upon.
The verb читать (to read) takes a direct object (what is being read).
In Девушка читает книгу, the girl is reading what? → книгу.

For feminine nouns ending in -а or -я (like книга, машина, газета), the accusative singular is usually formed by changing:

-а → -у: книга → книгу, машина → машину
-я → -ю: статья → статью, история → историю

Why is it в парке and not в парк or на парке?

The preposition в can take either the prepositional or accusative case, depending on meaning:

в парке (prepositional case) = in the park (location, where?)
в парк (accusative case) = into the park (direction, where to?)

In this sentence, the girl is already in the park, reading there, so we talk about location, not movement:

Где девушка читает книгу? – В парке. → prepositional case парке.

Why not на парке?

на is used with some places (на улице – in the street, на работе – at work), but with парк the natural, standard choice is в парке. You say в парке = in the park.

Why is it парке and not парк after в?

After в, when you talk about location (where?), you usually need the prepositional case.

The basic form (nominative) is:

парк (park)

Prepositional singular for most masculine nouns ending in a consonant is formed by adding -е:

парк → в парке (in the park)
город → в городе (in the city)
лес → в лесу (in the forest; this one is irregular)

So:

в парк (accusative) = into the park (direction, movement)
в парке (prepositional) = in the park (location)

What is the infinitive form of читает, and how is it conjugated?

The infinitive is читать = to read.

Читает is 3rd person singular, present tense (he/she/it reads, is reading).

Present tense conjugation of читать:

я читаю – I read / I am reading
ты читаешь – you (singular, informal) read
он / она / оно читает – he / she / it reads
мы читаем – we read
вы читаете – you (plural or formal) read
они читают – they read

In our sentence:

Девушка = she → она читает.

How do you say “is reading” in Russian? Why is there no word for is?

Russian does not use a separate verb like to be in the present tense for simple statements.

English: The girl is reading a book.
Russian: Девушка читает книгу. (literally “The girl reads a book.”)

The present tense of the main verb читает covers both:

reads (habitually)
is reading (right now)

Context usually tells you which one is meant. There is no need for “is” in Russian present tense sentences like this.

How can I tell if девушка means “girl” or “young woman”?

The word девушка can mean:

girl (often teenage girl)
young woman (unmarried, usually fairly young)

The exact nuance depends on context and age. In many contexts it’s closer to young woman rather than a little girl.

For a small child (a little girl), Russians are more likely to say:

девочка – (little) girl

So:

девочка читает книгу – a (little) girl is reading a book
девушка читает книгу – a young woman / a (older) girl is reading a book

Why is there no word for a or the in the Russian sentence?

Russian has no articles (a, an, the). The noun девушка, книга, парк can be understood as:

a girl, a book, a park
or the girl, the book, the park

Which one is correct depends on context, not on a special word.

In isolation:

Девушка читает книгу в парке. is most naturally understood as
A girl is reading a book in a park.

With previous context, it could refer to the girl / the book / the park already known to both speakers.

What gender are девушка, книга, and парк, and how can I tell?

девушка – feminine
книга – feminine
парк – masculine

Basic rules for gender (nominative singular):

Feminine: usually end in -а or -я
- девушка, книга, машина, история
Masculine: usually end in a consonant
- парк, стол, дом, город
Neuter: usually end in -о or -е
- окно, море, поле

There are exceptions, but this works for most nouns.

How do the cases work for all three nouns in this sentence?

In Девушка читает книгу в парке, we have:

Девушка – nominative case
- It is the subject (who is doing the action?).
- Question: Кто читает? – Девушка.
книгу – accusative case
- It is the direct object (what is being read?).
- Question: Что она читает? – Книгу.
в парке – prepositional case
- Used after в (and some other prepositions) to show location (where something is happening).
- Question: Где она читает книгу? – В парке.

So you see three different cases in one simple sentence:

Nominative: девушка
Accusative: книгу
Prepositional: в парке

Can I change the word order? For example, is В парке девушка читает книгу correct?

Yes, Russian word order is more flexible than English, though it can change the emphasis.

These are all grammatically correct:

Девушка читает книгу в парке.
– neutral; basic information: who does what where.
В парке девушка читает книгу.
– emphasizes where; “In the park, a girl is reading a book.”
Девушка в парке читает книгу.
– slight focus on the fact that it’s the girl in the park (not somewhere else) who is reading.
Книгу читает девушка в парке.
– sounds more poetic or emphatic, highlighting книгу or девушка depending on context.

The grammatical roles are shown mainly by endings (cases), not by position, so you can move words more freely than in English. However, for beginners, the safest neutral order is:

Subject – Verb – Object – Place
→ Девушка читает книгу в парке.

Is читает imperfective or perfective? How would the perfective form change the meaning?

Читает comes from the imperfective verb читать.

Imperfective describes:

ongoing actions,
repeated actions,
processes in general.

So Девушка читает книгу can mean:

She is reading the book (process, right now).
She reads the book (habitually / generally).

The perfective partner is прочитать – to read (finished, to have read).

Future perfective forms:

Девушка прочитает книгу. – The girl will read (will finish reading) the book.

This focuses on completion of the action, not the process. You cannot normally use perfective in the present for an ongoing action; its “present forms” usually refer to the future.