Learn Hardcore Russian: Книга лежит рядом с её домом.

The sentence breaks down as follows: • Книга – “book” (subject in the nominative case). • лежит – “lies” or “is lying” (the third-person singular form of the verb лежать indicating a horizontal position). • рядом – “next to” or “nearby” (an adverb describing location). • с её домом – a prepositional phrase where с (“with” or “next to”) requires the noun that follows to be in the Instrumental case; её means “her” (a possessive pronoun that remains the same across cases), and домом is the Instrumental form of дом (“house”). Altogether, the sentence translates as: “The book is lying next to her house.”

Why is the noun дом changed to домом in this sentence?

In Russian, many prepositions govern specific cases. The preposition с in the expression рядом с requires that the following noun be in the Instrumental case. Hence, дом (nominative) becomes домом when it follows с. This rule is essential for indicating location or association using this construction.

How does the possessive pronoun её function here, and why does it remain unchanged?