This is the 53rd most frequent Japanese word.
山口
"Yamaguchi" means "mountain entrance" or "mountain mouth."
In this sentence, '山口' refers to a location in Japan, specifically a prefecture named Yamaguchi.
山口は美しい景色で有名です。
Yamaguchi is famous for its beautiful scenery.
'山口' in this context is a common Japanese surname referring here to a specific person.
山口さんにメールを送りました。
I sent an email to Mr./Ms. Yamaguchi.
Here, '山口' literally means 'mountain entrance,' using its direct translation of '山' as 'mountain' and '口' as 'mouth/entrance.'