A cyclotomic number is a complex number 
that lies on and is one of a sequence of numbers that divides
the unit circle in the complex
plane 
into an equal number of parts. More generally, the term may be used for a complex
number that is closely related to such a number.
The roots of unity, known as de Moivre numbers, are the most common cyclotomic numbers,. The Sylvester cyclotomic numbers are a more complicated variant related to Lucas sequences.
