shinshitsu no mado o akeru to kaze ga haitte, aratta shiitsu ga yoku kawakimasu.

When I open the bedroom window, air comes in, and the washed sheets dry well.

Breakdown of shinshitsu no mado o akeru to kaze ga haitte, aratta shiitsu ga yoku kawakimasu.

• を: direct object particle
• が: subject particle
• の: possessive case particle
• と: conditional particle

Questions & Answers about shinshitsu no mado o akeru to kaze ga haitte, aratta shiitsu ga yoku kawakimasu.

Why is の used in 寝室の窓?

の links two nouns. Here, 寝室の窓 means the bedroom window or more literally the window of the bedroom.

So:

• 寝室 = bedroom
• 窓 = window
• 寝室の窓 = bedroom window

This is one of the most common uses of の: showing possession, belonging, or a descriptive relationship between nouns.

Why is it 窓を開ける and not 窓が開ける?

Because 開ける is a transitive verb, meaning to open something. A transitive verb takes a direct object, and that object is marked by を.

So:

• 窓を開ける = open the window

If you wanted to say the window opens or the window is open/opened, you would use the intransitive verb 開く instead:

• 窓が開く = the window opens

This is a very common Japanese verb pair:

• 開ける = to open something
• 開く = something opens

What does ～と mean in 開けると?