Questions & Answers about У коробці дев’яносто книг.
Because after у/в meaning in, Ukrainian uses the locative case when talking about location.
The dictionary form is коробка (box), but in the locative singular it becomes коробці:
- коробка — nominative
- у коробці — locative, in the box
So у коробці is the correct form for in the box.
This is a normal case change for many feminine nouns ending in -ка.
When коробка goes into the locative singular:
- the ending -а changes
- the consonant к changes to ц
- the new ending is -і
So:
- коробка → коробці
That consonant change may look strange at first, but it is very common in Ukrainian declension.