Breakdown of Он сидел рядом со мной весь вечер.
он
he / it (for a masculine noun) / it (for a neuter noun)
я
I
сидеть
to sit
весь
all, the whole, everything, everyone
Questions & Answers about Он сидел рядом со мной весь вечер.
Why does the sentence use со instead of the usual preposition с?
We use со instead of с to make pronunciation easier when the next word begins with certain consonant clusters. Because мной starts with мн, saying с мной would be awkward, so the preposition adds an о and becomes со мной.
We've been learning spatial prepositions that take the Genitive, Accusative, and Dative. What case does рядом с take here?
It takes the Instrumental case. The phrase рядом с (next to) always requires the Instrumental case for the object you are next to. Here, мной is the Instrumental form of the pronoun я.
Why is весь вечер in the Accusative case if it isn't the direct object of the verb?
In Russian, the Accusative case is used without a preposition to show the duration of an action. Whenever you want to say how long something happened (like "all evening", "all day", or "for a week"), you put the time phrase in the Accusative.
Why is the imperfective verb сидел used here instead of a perfective verb, if the evening is already over?
Russian uses the imperfective aspect when highlighting the duration of an action. Because the sentence explicitly tells us how long he was sitting there (весь вечер), it focuses on the continuous process rather than a single completed result, so the imperfective сидел is required.