Larynx: A tube-shaped organ in the neck that contains the vocal cords. The larynx is about 5 cm (2 in.) long. It is part of the respiratory system and is located between the pharynx and the trachea. Humans use the larynx to breathe, talk, and swallow. Its outer wall of cartilage forms the area of the front of the neck referred to as the Adam's apple. The vocal cords, two bands of muscle, form a V inside the larynx. Each time a person inhales, air goes into the nose or mouth, then through the larynx, down the trachea, and into the lungs. When a person exhales, the air goes the other way. The vocal cords are relaxed during breathing, and air moves through the space between them without making any sound. The vocal cords tighten up and move closer together for speech. Air from the lungs is forced between them and makes them vibrate, producing the sound of a voice. The openings of the esophagus and the larynx are very close together in the throat. When a person swallows, a flap called the epiglottis moves down over the larynx to keep food out of the windpipe. Also known as voice box.