Generally speaking, an object with rotational symmetry is an object that looks the same after a certain amount of rotation

Rotation

A rotation is a circular movement of an object around a center of rotation. A three-dimensional object rotates always around an imaginary line called a rotation axis. If the axis is within the body, and passes through its center of mass the body is said to rotate upon itself, or spin. A rotation...

. An object may have more than one rotational symmetry

Symmetry

Symmetry generally conveys two primary meanings. The first is an imprecise sense of harmonious or aesthetically pleasing proportionality and balance; such that it reflects beauty or perfection...

; for instance, if reflections or turning it over are not counted, the triskelion

Triskelion

A triskelion or triskele is a motif consisting of three interlocked spirals, or three bent human legs, or any similar symbol with three protrusions and a threefold rotational symmetry. Both words are from Greek or , "three-legged", from prefix "τρι-" , "three times" + "σκέλος" , "leg"...

 appearing on the Isle of Man

Isle of Man

The Isle of Man , otherwise known simply as Mann , is a self-governing British Crown Dependency, located in the Irish Sea between the islands of Great Britain and Ireland, within the British Isles. The head of state is Queen Elizabeth II, who holds the title of Lord of Mann. The Lord of Mann is...

's flag (see opposite) has three rotational symmetries (or "a threefold rotational symmetry"). More examples may be seen below. The degree of rotational symmetry is how many degrees the shape has to be turned to look the same on a different side or vertex.