Learn Hardcore Russian: Учитель просит студентов не нервничать и улыбаться на экзамене. - The teacher asks the students not to be nervous and to smile during the exam.

Учитель просит студентов… = The teacher asks the students… (кого? студентов — genitive)
Она просит денег. = She asks (for) money. (чего? денег — genitive)

In English the object of ask is usually just in the objective case (asks the students), but in Russian просить кого takes the genitive form, not the accusative, even though it behaves like a direct object in meaning.

Why are не нервничать and улыбаться in the infinitive instead of conjugated (они не нервничают, они улыбаются)?

In Russian, when you say that someone is asking, telling, ordering someone to do / not to do something, you normally use the infinitive after verbs like:

просить — to ask
говорить — to tell (to do something)
приказывать — to order
советовать — to advise
запрещать — to forbid

The basic pattern is:

просить кого? что делать? — to ask whom? to do what?

So:

Учитель просит студентов не нервничать и улыбаться на экзамене.
The teacher asks the students not to be nervous and to smile in the exam.

If you wanted to use conjugated verbs (like they are not nervous, they smile), you would need a subordinate clause with чтобы:

Учитель просит, чтобы студенты на экзамене не нервничали и улыбались.
(literally: The teacher asks that the students should not be nervous and should smile in the exam.)

Why is it не нервничать и улыбаться, and not не нервничать и не улыбаться? Does the не apply to both verbs?

In this sentence, не clearly applies only to the first verb:

не нервничать — not to be nervous
улыбаться — to smile (a positive request)

So the meaning is: not to be nervous and (instead) to smile.

If you said:

Учитель просит студентов не нервничать и не улыбаться на экзамене.

that would mean: not to be nervous and not to smile — a strange instruction in this context.

There’s no automatic rule in Russian that one не always spreads over several verbs linked by и. Native speakers interpret it from context and from normal logic. Here, two opposite ideas (don’t be nervous / do smile) are intended, so не is only for нервничать.

Why are нервничать and улыбаться imperfective? When would you use perfective forms like понервничать, улыбнуться?

Here, the teacher is talking about general behavior during the exam, not about a single moment or a completed action. For ongoing, repeated, or habitual actions, Russian uses the imperfective aspect:

нервничать — to be nervous (as a state / process)
улыбаться — to smile (as a repeated or ongoing action)

So:

не нервничать и улыбаться на экзамене
= not to be nervous and to keep smiling / to smile in general during the exam.

Perfective would change the meaning:

понервничать — to be nervous for a while / get nervous once
улыбнуться — to smile once (to give a smile)

If you used perfective infinitives, it would sound like the teacher wants a one-time act:

просит студентов не понервничать и улыбнуться на экзамене
– sounds odd and unnatural in this context; it suggests some specific short events, not general behavior.

Could we say Учитель просит, чтобы студенты не нервничали и улыбались на экзамене instead? What’s the difference?

Yes, that sentence is grammatically correct and natural:

Учитель просит, чтобы студенты не нервничали и улыбались на экзамене.

Differences:

Original (infinitives):
- Учитель просит студентов не нервничать и улыбаться…
  Focuses more on the requested actions themselves. It’s a very typical pattern after просить.
With чтобы + past tense forms:
- Учитель просит, чтобы студенты не нервничали и улыбались…
  Literally: asks that the students not be nervous and (that they) smile.
  This structure emphasizes the desired situation/state of the students a bit more.

In everyday speech, both are used. The infinitive version often feels slightly more direct and “request-like”; the чтобы version can sound a bit more formal or explanatory, but the difference is subtle.

What is the difference between на экзамене and на экзамен?

They use different cases and express different ideas:

на экзамене — at the exam, during the exam
- на + Prepositional = location / time within some event
- на экзамене answers “где? когда?” (where? when?)
на экзамен — to the exam (to go, to come, to sign up for the exam, etc.)
- на + Accusative = direction, goal
- на экзамен answers “куда?” (to where?)

Compare:

Он нервничает на экзамене. — He is nervous in the exam / during the exam.
Он идёт на экзамен. — He is going to the exam.

In the original sentence we are talking about behavior during the exam, so на экзамене is the correct form.

Why do we use на (на экзамене) and not в (в экзамене)?

With events, activities, and public occasions, Russian very often uses на, not в:

на уроке — in class
на концерте — at a concert
на совещании — at a meeting
на экзамене — at an exam

So this is a lexical pattern: certain nouns just typically take на in this “at/during the event” meaning.

В экзамене would sound wrong in standard Russian in this context.

Is the word order fixed? Can we move parts of the sentence around?

Russian word order is relatively flexible, but there is a neutral, most natural order:

Учитель просит студентов не нервничать и улыбаться на экзамене.

Basic pattern: Subject – Verb – Object – Other parts.

Other orders are possible but change emphasis or may sound awkward:

Студентов учитель просит не нервничать и улыбаться на экзамене.
Emphasizes студентов (as opposed to someone else).
Учитель на экзамене просит студентов не нервничать и улыбаться.
Emphasizes that he asks at the exam.

But something like:

Не нервничать и улыбаться на экзамене просит студентов учитель.

sounds quite unnatural and stylistically strange in normal speech. So yes, you can rearrange, but the given word order is the most standard and neutral.

How would you turn this into a direct command to the students in Russian?

A direct command uses the imperative:

Не нервничайте и улыбайтесь на экзамене.
= Don’t be nervous and smile in the exam.

Here:

не нервничайте — 2nd person plural (or polite) imperative of нервничать
улыбайтесь — 2nd person plural imperative of улыбаться

So the original sentence is indirect speech:

Учитель просит студентов: „Не нервничайте и улыбайтесь на экзамене.“

Why does учитель without any article mean “the teacher” and not just “a teacher”?

Russian has no articles (a, an, the). A bare noun like учитель can correspond to a teacher or the teacher, depending on context.

In this sentence:

Учитель просит студентов…

we naturally interpret учитель as the teacher who is known from context (e.g. their teacher or the exam teacher). If this were introducing some random, unknown teacher, English might say a teacher asks…, but Russian uses the same form учитель; the specificity is inferred from situation, not from articles.