The yo-yo is a toy consisting of two equally-sized discs of plastic,
wood, or metal, connected with an axle, around which string is wound.
There is a slip knot at the free end of the string, and, on a properly
strung yo-yo, an uncut loop around the axle end which allows it
to spin freely, or "sleep" upon reaching the string's
It is played by tying the string's free end around the middle finger,
grasping the yo-yo, and then throwing it downwards with a smooth
motion. As the axle spins within the loop, a gyroscopic effect occurs,
permitting time to perform a number of movements. By flicking the
wrist, the yo-yo can be made to return to the player's hand, with
the cord again completely wound into the groove. Any movement, or
combination of movements, which result in the return of the yo-yo
to the player's hand in this fashion is considered a trick.
Yo-yoing is a popular pastime around the world. Although generally
associated with children, it is not uncommon for people who gain
a level of proficiency at the sport in youth to continue playing
into adulthood. A Yo-yo player is referred to as a Yo-yoer.