Я купил носки дёшево, но забыл их дома.

I bought socks cheaply but forgot them at home.

Breakdown of Я купил носки дёшево, но забыл их дома.

• я: I
• купить: to buy
• дома: at home
• но: but

Questions & Answers about Я купил носки дёшево, но забыл их дома.

Why is дёшево not changing its ending like an adjective would?

Because дёшево is an adverb modifying the verb купил, not an adjective modifying носки. Adverbs in Russian are indeclinable, so дёшево stays the same regardless of gender, number or case.

What case is носки in, and why?

Носки is in the accusative plural. Since купил is a transitive verb that takes a direct object, the object носки goes into the accusative. For inanimate nouns, the accusative plural looks the same as the nominative plural.

Why is there no preposition before дома in забыл их дома?

In Russian, when you say you left something at a location, you often use the locative meaning of дома without a preposition. Дома here is a positional adverb (“at home”). If you used a preposition (like в), you’d have to switch to a case: в доме, but that feels more formal or specific (“inside the house”) rather than the idiomatic “at home.”

Why do we use их here instead of repeating носки?

Их is the accusative plural pronoun for “them.” Since носки are the direct object and they’ve just been mentioned, Russian replaces them with их to avoid repetition, precisely as English does with “them.”