Chiroptera is the name of the order of the only mammal capable of true flight, the bat. The name is influenced by the hand-like wings of bats, which are formed from four elongated "fingers" covered by a cutaneous membrane. It is based on the Greek words for "hand," "cheir," and "wing," "pteron." "Cheir" also had a hand in the formation of the word surgery, which is ultimately derived from the ancient word cheirourgos, meaning "doing by hand." "Pteron" is widely used in technical names of flying insects. It’s also the ancestor of a well-known, common word: "helicopter," which joins "pteron" with Greek heliko, meaning "spiral."