Breakdown of Механик вернулся в гараж за дубликатом ключа и запчастью.
и
and
ключ
key
в
in / to (direction)
вернуться
to return (pf)
Questions & Answers about Механик вернулся в гараж за дубликатом ключа и запчастью.
Why do we use за дубликатом instead of для дубликата in this sentence?
In Russian, when you go somewhere to fetch, retrieve, or pick up an object, you use the preposition за followed by the Instrumental case. You would use для plus the Genitive case if the object were intended for someone's benefit. Since the mechanic is moving to retrieve these items, за is required.
Why is ключа in the Genitive case if the preposition за triggers the Instrumental?
The preposition за only affects the main object being retrieved, which is дубликатом. The word ключа is in the Genitive case because it describes what the duplicate is of. In Russian, this descriptive relationship uses the Genitive case for the second noun, completely independently of the case the first noun is in.
Why does the second item being fetched end in -ью as запчастью?
Its dictionary form запчасть is a feminine noun ending in a soft sign, belonging to the third declension class just like вещь or ночь. In the Instrumental case, these nouns take the ending -ью. It must be in the Instrumental case here because it is connected by и to the first item, meaning it is still governed by the preposition за.
Where does the word запчасть come from?