Er spricht höflich mit dem Nachbarn.

He speaks politely with the neighbor.

Breakdown of Er spricht höflich mit dem Nachbarn.

• mit: with
• er: he
• sprechen: to speak
• der Nachbar: the neighbor
• höflich: politely

Questions & Answers about Er spricht höflich mit dem Nachbarn.

Why is dem Nachbarn used (why dem and why -n on Nachbarn)?

Preposition mit always requires the dative case. The masculine article der changes to dem in dative. Additionally, Nachbar is a weak masculine noun (n-declension), so it takes -n (or -en) in all cases except nominative singular. Hence dem Nachbarn.

What part of speech is höflich in this sentence? Should it have an adjective ending?

Here höflich functions adverbially, describing how he speaks. In German, adjectives used as adverbs are not declined; they remain in their base form. So Er spricht höflich = He speaks politely.

Why is höflich placed immediately after the verb spricht and before mit dem Nachbarn?

German word order generally places adverbs of manner right after the finite verb. Complements such as prepositional phrases then follow, so the natural order is spricht + höflich + mit dem Nachbarn.

Can I replace sprechen with reden here? Would it change the meaning?

Yes. reden is a close synonym of sprechen in the sense to talk.
Example: Er redet höflich mit dem Nachbarn.
Nuance: reden is slightly more colloquial; sprechen feels a bit more formal.

What’s the difference between sprechen mit someone and sprechen zu someone?

• sprechen mit + Dative means to speak with or have a conversation with someone.
• sprechen zu + Dative means to address someone, often in a more one-way or formal context (e.g. giving a speech).
Both constructions require the dative case (e.g. mit dem Kind, zu dem Kind).

How do I turn Er spricht höflich mit dem Nachbarn. into a yes/no question?

Invert the subject and the finite verb:
Spricht er höflich mit dem Nachbarn?