This is the 16963rd most frequent Russian word.
соседом
"Соседом" means "neighbor" (instrumental case in Russian).
In this sentence, 'соседом' is used in instrumental case as it describes the person accompanying the action of walking.
Я гулял вчера с соседом в парке.
I walked yesterday with the neighbor in the park.
Here, 'соседом' is in instrumental case, showing involvement or association with the action of discussing.
Мы обсудили проблему строительства дома с соседом.
We discussed the problem of building a house with the neighbor.
In this example, 'соседом' is used in instrumental case, indicating the entity involved in the context of the meeting.