Laughter is a pleasant physical reaction and emotion consisting usually of rhythmical, often audible contractions of the diaphragm and other parts of the respiratory system. It is a response to certain external or internal stimuli.

Laughter is the physiological respo­nse to humor. Laughter consists of two parts -- a set of gestures and the production of a sound. When we laugh, the brain pressures us to conduct both those activities simultaneously. When we laugh heartily, changes occur in many parts of the body, even the arm, leg and trunk muscles.

Laughter is a person’s physiological reaction to hearing or seeing something humorous or funny. It is essentially a repeating set of sounds, like “Ha ha.” Laughter has a calming effect on us, and may actually put us more at ease in the presence of another person.