Learn Hardcore Russian: В лесу нельзя бросать мусор. - In the forest, it is not allowed to throw trash.

In В лесу нельзя бросать мусор, it expresses a general prohibition:
“You must not throw rubbish in the forest / It’s forbidden to throw rubbish in the forest.”

It does not mean “physically impossible”; it’s about rules, norms, or something being unacceptable.

Why is it в лесу and not в лесе?

В лесу uses a special old locative form of the prepositional case.
Some common nouns of place have two prepositional forms:

в лесе – “in the forest” (neutral, descriptive)
в лесу – also “in the forest”, but often used for real, physical location, especially in set phrases and everyday speech.

For many locations, Russian prefers the locative form in natural-sounding phrases:

в лесу – in the forest
в саду – in the garden
в шкафу – in the cupboard
на полу – on the floor

In this sentence, в лесу is the normal, idiomatic choice.

What case is лесу, and what does the ending -у show?

Лесу is in the prepositional case, singular, masculine.

The prepositional singular ending is usually -е (лес → в лесе), but a group of masculine nouns of location (лес, сад, дом, рай, etc.) also have a special locative ending -у / -ю used mainly after в or на to say “in/at (this place)” in a more concrete, spatial sense.

So:

лес (nominative) – “forest”
в лесу – “in the forest” (prepositional, locative form)

Why is there no subject like “you” or “people” in Russian?

Russian often uses impersonal constructions for general rules and prohibitions.

В лесу нельзя бросать мусор literally is something like:
“In the forest, it-is-not-allowed to-throw rubbish.”

There is no grammatical subject; it’s just an impersonal statement of prohibition. English needs a subject, so we translate it as:

“You must not throw rubbish in the forest.”
“People must not throw rubbish in the forest.”
“Throwing rubbish in the forest is not allowed.”

All of these are valid translations of the same Russian impersonal structure.

Why is the verb бросать in the infinitive, and what aspect is it?

Бросать is the imperfective infinitive.

For general rules, habits, permissions, and prohibitions, Russian normally uses the imperfective:

Здесь можно курить. – You may smoke here.
Здесь нельзя парковаться. – You must not park here.
В лесу нельзя бросать мусор. – You must not throw rubbish in the forest (in general, ever).

If you used the perfective бросить, it would sound like “to throw once / to have thrown”, which doesn’t fit a general rule.

Can I say В лесу нельзя бросить мусор instead? What’s the difference?

You can say В лесу нельзя бросить мусор, but it means something different and sounds strange for a sign or rule.

В лесу нельзя бросать мусор.
General prohibition: “You must not throw rubbish in the forest (in general).”
В лесу нельзя бросить мусор.
Implies impossibility or inability to complete the action even once.
Context example: “You can’t throw rubbish in the forest (because there is nowhere to put it / conditions make it impossible).”

For rules and signs, always use the imperfective: нельзя + бросать.

What case is мусор, and is it countable in Russian?

In the sentence В лесу нельзя бросать мусор:

мусор is masculine inanimate, singular,
here it is in the accusative case, but for masculine inanimate nouns, the accusative looks the same as the nominative (мусор → мусор).

As a noun, мусор is generally uncountable, similar to English “trash” or “rubbish”:

много мусора – a lot of rubbish (genitive singular)
убрать мусор – to clean up the rubbish

If you need to count individual pieces, you count “bags” or “pieces” of rubbish, not мусоры in normal speech.

How is the word order chosen? Could I say Нельзя бросать мусор в лесу?

Yes, you can say:

В лесу нельзя бросать мусор.
Нельзя бросать мусор в лесу.

Both are grammatically correct and natural. The difference is in focus:

В лесу нельзя бросать мусор.
Slight emphasis on in the forest (there specifically).
Нельзя бросать мусор в лесу.
More neutral or slightly focused on the prohibition itself.

Russian word order is flexible. Elements often move to the beginning of the sentence for emphasis, but the core meaning stays the same.

What’s the difference between нельзя бросать мусор and an imperative like не бросайте мусор?

Both express prohibition, but style and tone differ:

В лесу нельзя бросать мусор.
Impersonal, general rule, neutral and formal. Often found on signs, rules, textbooks.
Не бросайте мусор в лесу.
Imperative, direct address to you (plural/formal). Slightly more personal: “Don’t throw rubbish in the forest.”

A sign might use either, but нельзя + infinitive sounds especially standard and impersonal.

Does в лесу mean one specific forest, or forests in general?

In Russian, the singular can often express a generic meaning about a type of place.

В лесу нельзя бросать мусор can mean:

“You must not throw rubbish in the forest (this forest we’re talking about now).”
Or more generally: “You must not throw rubbish in forests.”

Context decides whether it’s about a specific forest or forests in general. The Russian sentence itself doesn’t force that difference strongly.

How do you pronounce В лесу нельзя бросать мусор?

Approximate phonetic transcription (IPA-like):

В лесу – [в лʲɪˈсу]
нельзя – [нʲɪлʲˈзʲa]
бросать – [брɐˈсатʲ]
мусор – [ˈмусər]

Features to notice:

в лесу: the в is very short, almost just softening л; е in ле- reduces to [ɪ].
нельзя: the льз cluster is soft; stress on -зя.
бросать: stress on -сать; final ть is soft.
мусор: stress on the first syllable; the unstressed о sounds closer to [ə].

Are there synonyms for мусор in this context?

Yes, but мусор is the most common and neutral word. Other options:

отходы – “waste”, more formal/technical.
сор – “trash/dirt”, more literary or specific.
мусор и отходы – “trash and waste” (legal/official style).

On a sign in a forest, мусор is exactly what you’d expect.