This is the 172nd most frequent Ukrainian word.
столиці
Capitals.
In this sentence, 'столиці' is the grammatically correct form of the root noun 'столиця' (meaning capital city) in the instrumental case, as it follows the preposition 'є'. This usage occurs when specifying that something (Kyiv) serves as a capital.
Київ є столицею України.
Kyiv is the capital of Ukraine.
Here, 'У столиці' means 'in the capital' and utilizes the noun 'столиця' in the locative case, which is typical following the preposition 'у' (in) to indicate location.
У столиці завжди є багато цікавих місць для відвідування.
There are always many interesting places to visit in the capital.
In this context, 'центрі столиці' combines the locative case 'центрі' (center) with the genitive case 'столиці' to specify that the event took place in the center of the capital city.