Learn Hardcore Russian: В аптеке можно купить витамин C.

аптека is the dictionary form (nominative case: “a pharmacy”).
After the preposition в with the meaning “in, at (location)”, Russian uses the prepositional case.
The prepositional case of аптека is аптеке (ending -е).

So:

аптека – pharmacy (subject form)
в аптеке – in/at the pharmacy (location)

Why is it в аптеке and not в аптеку?

Both exist but mean different things:

в аптеке – in/at the pharmacy (location, where something happens)
- В аптеке можно купить витамин C. – You can buy vitamin C in the pharmacy.
в аптеку – into the pharmacy / to the pharmacy (direction, where you are going)
- Я иду в аптеку. – I’m going to the pharmacy.

So:

в + prepositional (в аптеке) → location (“in/at”)
в + accusative (в аптеку) → direction (“into/to”)

What exactly does можно mean here, and why is there no subject like “I” or “you”?

Можно is an impersonal modal word meaning “it is possible / one can / it is allowed”.

In В аптеке можно купить витамин C. there is no grammatical subject.
The idea is general: “One can buy vitamin C in a pharmacy” / “You can buy vitamin C in a pharmacy.”

You can specify for whom it is possible by adding a dative:

Мне можно купить витамин C. – I am allowed to buy vitamin C.
Тебе можно купить витамин C. – You are allowed to buy vitamin C.

But in the original sentence, it’s just a general statement about possibility.

Why is купить in the infinitive and not a conjugated form like куплю or покупаю?

After можно, Russian normally uses the infinitive:

можно + infinitive = it is possible / allowed to do X

So:

можно купить – (one) can buy
можно поесть – (one) can eat
можно войти – (one) can enter

A personal form like куплю (“I will buy”) would need a subject and would not match the impersonal construction with можно:

✅ Здесь можно купить витамин C. – You can buy vitamin C here.
✅ Я куплю витамин C. – I will buy vitamin C.
❌ Здесь можно куплю витамин C. – ungrammatical.

What is the difference between купить and покупать here? Could I say можно покупать витамин C?

Yes, both verbs exist, but they differ in aspect:

купить – perfective: to buy once / as a completed action
покупать – imperfective: to buy repeatedly, habitually, or as a process

In this sentence:

можно купить витамин C → you can (go and) buy vitamin C (a specific act of buying, treated as a single completed action).

If you say:

В аптеке можно покупать витамин C.

This usually sounds like:

“It is allowed/okay to buy vitamin C (here or in general),”
or
“You can regularly/habitually buy vitamin C in the pharmacy.”

So:

купить – focus on one act of purchase.
покупать – focus on permission or repeated action.

Why is there no word for “a” or “the” in в аптеке and витамин C?

Russian has no articles (no direct equivalents of a/an or the).

The same noun form can mean “a/an …”, “the …”, or refer to things in general. Context gives the nuance.

в аптеке can be understood as “in a pharmacy” or “in the pharmacy”, depending on context.
витамин C can mean “vitamin C (in general)” or “the vitamin C” you are talking about.

So the sentence can be translated naturally as:

“You can buy vitamin C at a pharmacy.”
“You can buy vitamin C at the pharmacy.”

Both are acceptable translations of the same Russian sentence.

What case is витамин C in, and why doesn’t the form change?

Витамин C is the direct object of купить, so it is in the accusative case.

However, витамин is:

masculine,
inanimate.

For masculine inanimate nouns, the accusative form is identical to the nominative:

Nominative: витамин – vitamin
Accusative: витамин – (to buy) a vitamin

So it is accusative here; it just looks the same as the dictionary form.

Can the word order be changed? For example, can I say В аптеке витамин C можно купить or В аптеке можно витамин C купить?

Yes, Russian word order is flexible, though some orders sound more neutral than others.

Most neutral/common versions:

В аптеке можно купить витамин C.
В аптеке можно купить витамин C. (this is the original)

Also fine:

В аптеке можно купить витамин C. – neutral, focuses first on place, then on possibility.
Витамин C можно купить в аптеке. – focuses first on what you can buy.

Less common but still grammatical:

В аптеке витамин C можно купить. – extra emphasis on витамин C.
В аптеке можно витамин C купить. – slightly colloquial, emphasizing that it is exactly vitamin C you can buy.

In everyday speech, the original sentence is the most straightforward and natural.

How do Russians normally write and pronounce витамин C?

In Russian, it is usually written as витамин С with the Cyrillic letter С, which corresponds to the sound [s].

When referring to the letter itself:

The Russian letter С is named “эс”.
So people say витамин эс (transliteration: vitamin es).

In continuous speech, you will hear something like:

[витам’ин эс] – vitamin es.

So:

Written: витамин С
Said: витамин эс

Why is there no personal subject like “они продают” (“they sell”) instead of можно купить? Could I say В аптеке продают витамин C?

Yes, you can say:

В аптеке продают витамин C. – “They sell vitamin C at the pharmacy.”

The difference in nuance:

В аптеке можно купить витамин C.
- Focus on possibility for you / people: you can go there and buy it.
- Impersonal, sounds like general information.
В аптеке продают витамин C.
- Focus on what the pharmacy does: they sell vitamin C.
- Grammatically has an implied subject они (“they”), even though it is not explicitly stated.

Both are correct; the original phrasing emphasizes what is possible rather than what they do.