Когда в комнате душно, я иду к окну и открываю его.

When it is stuffy in the room, I go to the window and open it.

Breakdown of Когда в комнате душно, я иду к окну и открываю его.

• я: I
• в: in
• комната: the room
• и: and
• к: to
• окно: the window
• когда: when
• открывать: to open
• его: it
• душно: stuffy
• идти: to go / to walk

Questions & Answers about Когда в комнате душно, я иду к окну и открываю его.

Why does the sentence start with Когда, and does it mean when or if here?

Когда introduces a time clause and normally means when (a time condition), not if (a hypothetical condition). In this kind of sentence it usually implies something habitual/typical: “Whenever it’s stuffy in the room, I …”.
For a more hypothetical “if,” Russian typically uses если.

Why is there a comma after душно?

Russian separates a subordinate clause from the main clause with a comma.
Here, Когда в комнате душно is the subordinate clause, and я иду к окну и открываю его is the main clause, so the comma is required.

What is душно grammatically? It looks like an adjective but there’s no noun.

Душно is a “category of state” word (a predicative adverb) used in impersonal sentences: душно = “(it is) stuffy.”
Russian often expresses “it is + adjective” without a verb, especially for weather/conditions: холодно, жарко, темно, душно, etc.

Why is there no word for is (like “it is stuffy”)?

In the present tense, Russian usually omits the verb быть (“to be”).
So в комнате душно literally is “in the room (is) stuffy,” with is understood.

Why is it в комнате and not something like комната душная?

в комнате душно focuses on the state/condition inside the room: “it’s stuffy in the room.”
комната душная describes the room as having the quality “stuffy” (like a “stuffy room” as a general characteristic). Both can be correct, but the impersonal pattern (в комнате + душно) is very common for temporary conditions.

What case is комнате in, and why?

комнате is in the prepositional case because of the preposition в meaning “in/inside” (location).
Basic pattern: в + prepositional for location: в комнате, в доме, в городе.

Why is к окну used instead of в окно?

к means “to/toward (up to)” and takes the dative: к окну = “to the window” (approaching it).
в окно usually means “into/through the window” (movement into something, or “out the window” depending on context), not simply going up to it.

What case is окну in?

окну is dative singular of окно after к.
Declension: окно (nom/acc) → окну (dat).

Why are the verbs иду and открываю in the present tense if the sentence is about a repeated action?

Russian often uses the present tense of imperfective verbs to describe habitual actions: “When it’s stuffy, I (usually) go… and (usually) open…”.
It functions like the English “I go / I open” for routine behavior.

Why is it иду, not хожу?

Both relate to “go on foot,” but they differ in meaning:

• идти (иду): going in one direction / one trip / a specific instance (“I go (over there)”).
• ходить (хожу): going around or habitually in a more general sense (“I go (regularly), I walk”).

In this sentence, иду к окну feels like “I go over to the window (each time),” a repeated single-direction action triggered by the condition.

Why is его used for “it”? Окно is neuter—shouldn’t it be something else?

For the object pronoun “it,” Russian uses forms that depend on the pronoun paradigm, not a special neuter-only word in the accusative:

• он → его (masc/neuter accusative for inanimate in many contexts)
• оно → его is also common in object position for “it” (neuter)

So открываю его = “I open it,” referring to окно. (For feminine nouns you’d get её, e.g., дверь → открываю её.)

What case is его here?

его is accusative (object) meaning “him/it,” used here as the direct object of открываю (“I open what? it.”).
It also looks identical to the genitive form (его), but in this sentence its function is clearly accusative.

Why is there no comma before и in я иду к окну и открываю его?

Because и connects two verbs (иду and открываю) that share the same subject (я) within one simple main clause. Russian doesn’t normally put a comma between two homogeneous predicates joined by и in this structure.

Could the sentence use perfective verbs like пойду and открою instead?

Yes, but it changes the meaning:

• Когда в комнате душно, я иду … и открываю … (imperfective) = a habitual/repeated response.
• Когда в комнате будет душно, я пойду … и открою … (perfective + future) = a specific future situation: “When it gets stuffy, I’ll go… and open…”.
  Using perfective in the present is not possible for these verbs; perfective would typically appear as future forms (пойду, открою).