island 普通用词，指一般的岛屿，即海里被水环绕、面积比大陆小的陆地，或河、湖中被水环绕的陆地。
peninsula 指三面临水一面连接大陆地，即半岛。
参考例句
1. Near the Florida Peninsula, there live lots of dolphins. 佛罗里达半岛附近省份存折很多海豚。
2. Video from the air shows the destruction Hurricane Ike had on the Bolivar Peninsula in Texas. 空中影像显示飓风艾克对得克萨斯州的玻利瓦尔半岛造成的破坏。
3. Shandong province has therefore set up the Jiaodong peninsula manufacturing base in hope of propelling its economic growth by the rapid development of the base. 山东省确立建设胶东半岛制造业基地，希望通过胶东半岛制造业的快速发展推动全省经济的更快发展。
英英解释
n.
1. a large mass of land projecting into a body of water
