This is the 7748th most frequent Korean word.
하노이
Hanoi (capital city of Vietnam).
In this sentence, '하노이' is used as a proper noun referring to the city of Hanoi.
하노이는 베트남의 수도입니다.
Hanoi is the capital of Vietnam.
Here, '하노이' is part of a locative expression referring to the location 'Hanoi'.
내 친구는 하노이에서 살고 있어요.
My friend lives in Hanoi.
In this example, '하노이' is used to indicate the destination city of 'Hanoi' for travel.