This is the 164th most frequent Ukrainian word.
київ
Kyiv: The capital city of Ukraine.
Here, 'Київ' is a proper noun referring to the geographical entity, the capital city of Ukraine.
Київ є столицею України.
Kyiv is the capital of Ukraine.
In this sentence, 'Києва' is the genitive case of 'Київ', used in the context of travel or directionality (to Kyiv).
Ми плануємо подорож до Києва наступного літа.
We are planning a trip to Kyiv next summer.
Here, 'Київ' again functions as a proper noun, emphasizing the city's reputation and cultural significance.