tonari no inu wa yoru ni yoku hoeru node, nemurenaikoto ga arimasu.

The neighbor's dog often barks at night, so sometimes I can't sleep.

Breakdown of tonari no inu wa yoru ni yoku hoeru node, nemurenaikoto ga arimasu.

• は: topic particle
• 犬いぬ: dog
• の: possessive case particle
• に: time particle

Questions & Answers about tonari no inu wa yoru ni yoku hoeru node, nemurenaikoto ga arimasu.

What does 隣の犬 mean exactly? Is it the neighbor's dog or the dog next door?

It can mean either, depending on context.

• 隣 = next door / neighboring
• の links 隣 to 犬
• 犬 = dog

So 隣の犬 is literally the neighboring dog. In natural English, that often becomes either:

• the neighbor's dog
• the dog next door

Here, の is not only possession. It can also mean the X that belongs to / is connected with / is next to Y.

Why is there a は after 犬 instead of が?

は marks the topic of the sentence: as for the dog next door...

So the sentence is setting up 隣の犬 as the thing being talked about, and then saying something about it:

• 隣の犬は = as for the dog next door,
• 夜によく吠える = it often barks at night

If you used が instead, it would sound more like you are identifying or emphasizing the dog next door as the one that barks. That can be correct in some contexts, but は is more natural here for a general statement or complaint.

Why does the sentence use 夜に? Is に necessary?