Я говорю в микрофон.

I speak into the microphone.

Breakdown of Я говорю в микрофон.

• я: I
• говорить: to speak
• в: into
• микрофон: the microphone

Questions & Answers about Я говорю в микрофон.

Why is it в микрофон and not в микрофоне?

In Russian, в + accusative often means into / towards (direction), while в + prepositional usually means in / inside (location).

• в микрофон (accusative) = into the microphone → where your voice is going.
• в микрофоне (prepositional) = in the microphone → literally inside the microphone (almost never what you mean with speaking).

Verbs of speaking, shouting, shooting, etc. often use в + accusative to show the target or direction:

• говорить в микрофон – to speak into a microphone
• кричать в окно – to shout into the window
• стрелять в цель – to shoot at the target

So в микрофон is correct for “into the microphone.”

What case is микрофон in, and how can I tell?

Микрофон is in the accusative singular.

Clues:

1. The preposition в here means into, which normally takes the accusative.
2. Микрофон is a masculine inanimate noun. For such nouns:
   • Nominative singular: микрофон
   • Accusative singular: микрофон (same form as nominative)

So the form doesn’t change, but the function (case) is accusative because of в with a directional meaning.