Мой друг всегда входит в дом тихо.

My friend always enters the house quietly.

Breakdown of Мой друг всегда входит в дом тихо.

• друг: the friend
• дом: the house
• мой: my
• тихо: quietly

Questions & Answers about Мой друг всегда входит в дом тихо.

Why is it входит, not some other form like войти or входить?

Russian has three main things to distinguish here:

1. Infinitive (dictionary form): входить – “to enter (habitually, in general)”.
2. Perfective infinitive: войти – “to enter (once, as a complete act)”.
3. Conjugated form, 3rd person singular, present tense: он входит – “he enters / he is entering / he goes in”.

In the sentence Мой друг всегда входит в дом тихо:

• входит is 3rd person singular, imperfective, present tense.
• It matches мой друг (3rd person singular).
• Imperfective present is what Russian uses for regular, repeated actions (“always enters”).

So:

• входить – “to enter” (in general, not conjugated)
• он входит – “he enters / is entering” (this specific form)
• войти – used when you want to talk about a single completed action (“to go in (once)”).

Why is дом in the form дом, not доме? What case is it?