This is the 10208th most frequent Japanese word.
関谷
"関谷" (Sekiya) is a Japanese surname or place name.
In this sentence, '関谷' is a proper noun, specifically referring to a person's name.
関谷は私の友達です。
Sekiya is my friend.
Here, '関谷' is used as part of a place name, referring to 'Sekiya Station'.
関谷駅で電車を待っています。
I am waiting for the train at Sekiya Station.
In this sentence, '関谷' is utilized as a surname/title in conjunction with '教授' (professor).