This is the 9708th most frequent Japanese word.
英樹
"英樹" (Hideki) is a Japanese given name meaning "excellent tree" or "heroic tree."
In this sentence, '英樹' is used as a proper noun to refer to a person named Hideki.
英樹は公園でランニングをしています。
Hideki is running in the park.
Here '英樹' is used as a given name with the honorific 'さん' to address Mr. Hideki politely.
英樹さんの趣味は読書です。
Mr. Hideki's hobby is reading.
In this sentence, '英樹' refers to someone's name included within the explanation about having a friend.