Hypocycloid, a mathematical term, has several synonyms. Some of these synonyms include hypocycloidal curve, epitrochoid, and Rayleigh curve. A hypocycloid is a curve generated by a fixed point on a small circle rolling inside a larger circle. It is a geometric shape that has been used in various fields, such as engineering, architecture, and design. The Rayleigh curve is named after Lord Rayleigh, who introduced the curve to the world of physics. An epitrochoid is also a type of hypocycloid that is generated by a point on a circle rolling around another circle. While these words may be new to some, they are essential and valuable in their respective fields.