Breakdown of Моя покупка оказалась полезной.
мой
my
полезный
useful
покупка
the purchase
оказаться
to turn out to be
Questions & Answers about Моя покупка оказалась полезной.
Why is моя покупка in the nominative case (and not accusative)?
Because in this sentence “моя покупка” is the subject—the thing that “turned out.” In Russian, the subject of an intransitive verb is in the nominative case. Here оказаться (“to turn out”) is intransitive, so моя покупка remains nominative.
What does the suffix -ся in оказалась do?
The -ся (often written -сь after a vowel) is the reflexive/middle-voice marker. With оказаться it doesn’t mean “do something to yourself” but rather forms an intransitive verb meaning “to turn out” or “to prove to be.” The base verb оказать means “to render” or “to show,” while оказаться has the special meaning “to turn out.”
Why is the verb оказалась feminine?
The past tense form of Russian verbs agrees in gender and number with the subject. Since покупка is a feminine noun, the past tense of оказаться takes the feminine ending -лась, giving оказалась. (For reference: masculine оказался, neuter оказалось, plural оказались.)
What case is полезной, and how do you know?