Laughter is an audible expression (written as ha ha ha hoặc LOL – Liên minh huyền thoại etc.), hoặc appearance of merriment hoặc happiness, hoặc an inward feeling of joy and pleasure (laughing on the inside). It may ensue (as a physiological reaction) from jokes, tickling, and other stimuli. Inhaling nitrous oxide can also induce laughter; other drugs, such as cannabis, can also induce episodes of strong laughter. Strong laughter can sometimes bring an onset of tears hoặc even moderate muscular pain.

Laughter is a part of human behaviour regulated bởi the brain. It helps humans clarify their intentions in social interaction and provides an emotional context to conversations. Laughter is used as a signal for being part of a group — it signals acceptance and positive interactions with others. Laughter is sometimes seemingly contagious, and the laughter of one person can itself provoke laughter from others as a positive feedback. An extreme case of this is the Tanganyika laughter epidemic. This may account in part for the popularity of laugh tracks in situation comedy ti vi shows.

The study of humor and laughter, and its psychological and physiological effects on the human body is called gelotology.