The trachea, also known as the WINDPIPE, is an 8-letter word that is part of the respiratory system. It is a tube-like structure that connects the mouth and nose to the lungs, allowing air to pass through. The trachea is surrounded by cartilage rings that help keep it open. The term 'WIND' is a 4-letter word that is related to the trachea, as it is the air that passes through the trachea and into the lungs.