Plants are living organisms belonging to the kingdom Plantae. They include familiar organisms such as trees, herbs, bushes, grasses, vines, ferns, mosses, and green algae. Botanists have identified about 391,000 species of plants, defined as seed plants, bryophytes, ferns and fern allies. About 2,000 new plant species are discovered or described every year, but so far, only about 31,000 of the total species have at least one documented use. These include uses for food, medicine, recreation, genes, poisons, animal feed, and building material.