# Definition:Hypocycloid

## Definition

Let a circle $C_1$ roll around the inside of another (larger) circle $C_2$.

The locus of a given point on the circumference of $C_1$ is known as a hypocycloid.

### Generator

The circles $C_1$ and $C_2$ can be referred to as the generators of the hypocycloid.

### Stator

The circle $C_2$ can be referred to as the stator of the hypocycloid.

### Rotor

The circle $C_1$ can be referred to as the rotor of the hypocycloid.

### Cusp

A cusp of the hypocycloid is defined as a point where the hypocycloid meets the larger circle.

### Arc

An arc of the hypocycloid is defined as one of the curves between two of the cusps of the hypocycloid.

## Also see

• Results about hypocycloids can be found here.

## Linguistic Note

The hypo- prefix in the term hypocycloid comes from the Greek word meaning under or beneath.

The prefix can be seen in other common words, for example hypodermic, which literally means under the skin.