Breakdown of Kupiłam dwa kilo jabłek.
jabłko
apple
dwa
two
kupić
to buy (perfective)
kilo
kilo (spoken short form of kilogram)
Questions & Answers about Kupiłam dwa kilo jabłek.
Who is speaking in this sentence?
Why doesn't the word kilo change its ending after dwa?
The word kilo is a loanword and is usually treated as indeclinable in spoken Polish, meaning it doesn't change its ending. You say jedno kilo, dwa kilo, or pięć kilo. If you used the full, formal word kilogram, it would change endings normally (for example, dwa kilogramy).
Why is the word for apples jabłek instead of jabłka?
Whenever you talk about quantities, containers, or measurements (like a kilo, a liter, or a box), the noun being measured goes into the genitive case. Since you are buying two kilos of apples, you must use the genitive plural form, which is jabłek.
Where does the "e" in jabłek come from? The dictionary form is jabłko.
For neuter nouns ending in -o like jabłko, the genitive plural is formed by dropping that final vowel. This would leave a hard-to-pronounce cluster of consonants at the end (jabłk). To fix this, Polish inserts an extra "e" (called a mobile e) between the last two consonants, giving us jabłek.