An organism that belongs to the Kingdom Plantae (plant kingdom) in biological classification. The term is also loosely used to indicate any organism that is not an animal. In the most commonly accepted modern classification (the five-kingdom system), fungi, bacteria, and algae belong to the kingdoms Fungi, Monera, and Protista, respectively, rather than to the plant kingdom as they did in the outmoded two-kingdom system. The study of plants is called botany.