This is the 4527th most frequent Japanese word.
山野井
"山野井" (Yamanoi) is a Japanese surname, typically meaning "mountain field well."
Here, '山野井' refers to a person's surname, addressed formally with 'さん' attached at the end.
山野井さんは日本語を教えている教師です。
Mr. Yamanoi is a teacher who teaches Japanese.
In this sentence, '山野井' represents a place or regional name, likely used as a proper noun.
彼は山野井地方の自然が大好きです。
He loves the nature of the Yamanoi area.
Here, '山野井' is used as a surname belonging to an individual, combined with a given name.