This is the 2651st most frequent Japanese word.
東アジア
East Asia.
In this sentence, '東アジア' is used as a proper noun to refer to the region, serving as the grammatical subject of the sentence.
東アジアの気候は、その多様性が特徴です。
The climate of East Asia is characterized by its diversity.
Here, '東アジア' is part of a possessive phrase ('東アジアの歴史'), describing the history associated with the region.
彼は東アジアの歴史に詳しい。
He is knowledgeable about the history of East Asia.
In this use, '東アジア' is part of a compound noun ('東アジア諸国'), referring collectively to the countries within the region.