Rhachides is a term used in botany to describe the central axis or stem of a compound leaf or inflorescence. Synonyms for this word include rachis, peduncle, and axis. The rachis is often found in ferns, where it supports the frond or leaf, as well as in compound flowers, where it supports multiple flowers on a single stalk. The peduncle is typically used to describe the stem of a single flower or fruit, and the axis can refer to the main support structure of a plant, such as the stem or trunk. Regardless of the specific usage, these synonyms all describe the essential component of a plant that provides structural support and transportation of nutrients.