The Slinky is a helical spring toy invented by Richard T. James in the early 1940s. It can perform a number of tricks, including travelling down a flight of steps end-over-end as it stretches and re-forms itself with the aid of gravity and its own momentum; and appearing to levitate for a period of time after it has been dropped. These interesting characteristics have contributed to its success in its home country of the United States, and it has inspired many popular toys with Slinky-like components, in a wide range of countries.

A spring is a device consisting of an elastic but largely rigid material bent or molded into a form that can return into shape after being compressed or extended. Springs can store energy when compressed. In everyday use, the term most often refers to coil springs, but there are many different spring designs. Modern springs are typically manufactured from spring steel. An example of a non-metallic spring is the bow, made traditionally of flexible yew wood, which when drawn stores energy to propel an arrow.