Categories is a party game in which players have to think of instances of a specific category. The players sit in a circle either on the floor or at a large table and collectively establish a rhythm of six beats: slap slap (on the thighs), clap clap (with the hands), snap snap (by clicking their fingers).

The players must speak in turn clockwise around the circle on the snap beats, using the slap and clap beats to gather their thoughts. On a player's turn, he or she must name a new instance of the category or be eliminated. Eliminated players sit out, creating an ever-shrinking circle, until only one player remains.

Typically a category is not chosen in advance, but is specified by the third player to speak after the first player has said "Categories" and the second player has said "such as...". A demonstration game between five players will illustrate:

slap slap clap clap - Player 1: "Categories"
slap slap clap clap - Player 2: "such as..."
slap slap clap clap - Player 3: "Diseases" (everyone now knows the category)
slap slap clap clap - Player 4: "Cancer"
slap slap clap clap - Player 5: "Chickenpox"
slap slap clap clap - Player 1: "Measles"
slap slap clap clap - Player 2: "Athlete's foot"
slap slap clap clap - Player 3: "Balls" (this is not a disease; Player 3 is eliminated)
slap slap clap clap snap snap (Player 4 is laughing so hard at Player 3 she misses the beat and is eliminated)
slap slap clap clap - Player 5: "Tuberculosis"
slap slap clap clap - Player 1: "Schizophrenia"
slap slap clap clap - Player 2: "AIDS"
slap slap clap clap - Player 5: "Ebola"
slap slap clap clap - Player 1: "Emphysema"
slap slap clap clap - Player 2: "Herpes"
slap slap clap clap - Player 5: "Hiccups" (getting desperate, but the other players accept it)
slap slap clap clap - Player 1: "HIV" (this is considered a repetition of AIDS; Player 1 is eliminated)
slap slap clap clap - Player 2: "Malaria"
slap slap clap clap - Player 5: "Leukemia" (considered a repetition of Cancer; Player 5 is eliminated; Player 2 wins)