This is the 3180th most frequent Japanese word.
古川
"古川" (Furukawa) is a Japanese surname or place name meaning "old river."
Here, '古川' refers to a surname and is used as a proper noun referring to a teacher.
古川先生は歴史の授業を担当しています。
Ms. Furukawa teaches the history class.
In this context, '古川' refers to an unnamed old river as a conceptual term.
この村には古川が流れています。
An old river flows through this village.
Here, '古川' is utilized to indicate a person’s name, specifically the surname.