Questions & Answers about Когда мы жили в деревне, у нас была собака.
Why does the verb была end in an -а instead of being plural to match мы (we)?
When you say "we had" in Russian using the у нас structure, the literal meaning is "at us was a dog". The dog (собака) is the actual subject of the sentence. Since собака is a feminine noun, the past tense verb for "was" must take the feminine form была to match it.
Could I use the verb иметь (to have) and say мы имели собаку instead?
It would be understood, but native speakers rarely use иметь for owning everyday things like pets or objects. The structure used here (literally "at us was") is the standard, natural way to express possession in Russian.
Why is the imperfective verb жили used here instead of a perfective verb?
Living in the village was an ongoing state or a background setting for a period of time, not a single, quickly completed action. Imperfective verbs like жили are always used to describe these continuous past states and set the scene.
Why does the word for village change to деревне here?
Because you are describing a location (living in the village), the word needs to be in the Prepositional case. The preposition в (in) combined with the feminine noun деревня changes its ending from -я to -е.