This is the 1268th most frequent Japanese word.
宮沢
"Miyazawa" is a Japanese surname meaning "shrine river."
In this sentence, 宮沢 (Miyazawa) is used as a surname to refer to an individual, and さん (san) is an honorific used for politeness.
宮沢さんは昨日、新しい本を出版しました。
Mr. Miyazawa published a new book yesterday.
Here, 宮沢 (miyazawa) is understood contextually as describing an area related to a shrine, due to the association of 宮 meaning 'shrine' and 沢 meaning 'marsh' or 'valley'.
その神社の宮沢はとても美しいです。
The shrine's area is very beautiful.
In this statement, 宮沢賢治 refers to Kenji Miyazawa, a famous Japanese poet and author of children's literature, demonstrating its use as a full name.