The subfamily Papilionoideae is a group of flowering plants that belong to the legume family. This subfamily includes a diverse range of plants that are characterized by their unique floral structure, which is made up of five petals that are often arranged in the shape of a butterfly. Other common features of plants within this subfamily include nitrogen-fixing roots and the ability to form symbiotic relationships with soil bacteria. There are many synonyms for the subfamily Papilionoideae, including the Faboideae, the Papilionaceae, and the Leguminosae. Regardless of the name used to describe this group of plants, they all play important roles in ecosystems around the world.