This is the 16961st most frequent Russian word.
соседнее
Adjacent or neighboring.
The word 'соседняя' describes the noun 'улицу' (street) by specifying its relative position as being adjacent or next.
Мы решили исследовать соседнюю улицу.
We decided to explore the neighboring street.
The word 'соседнем' is in the locative case, describing the noun 'здании' (building) and indicating its proximity.
В соседнем здании находится библиотека.
In the neighboring building, there is a library.
The word 'соседние' is plural, modifying the noun 'дома' (houses) to specify that they are close to each other.