Pneu is a root word commonly used in medical terminology to refer to air or gas. It is derived from the Greek word pneuma, which means breath or wind. There are various synonyms for the word pneu, such as aer-, aero-, pneum-, and pneumo-. These prefixes and combining forms are used to create many medical terms, such as aerobics, meaning exercise that requires oxygen, or pneumothorax, which is the accumulation of air in the pleural cavity between the lung and chest wall. Understanding the different synonyms for pneu can aid in effectively communicating with medical professionals and understanding their terminology.