This is the 5388th most frequent Japanese word.
tokyo
Tokyo: The capital city of Japan.
Tokyo in this sentence is used as a proper noun referring to the city itself.
東京は日本の首都です。
Tokyo is the capital of Japan.
Tokyo is used as the destination in a sentence expressing desire to travel.
東京に旅行したいです。
I want to travel to Tokyo.
Tokyo is used as a compound noun forming part of the name of a specific location.