 The Archimedean spiral has two arms, one for "θ" > 0 and one for "θ"  (see contribution from Mikhail Gaichenkov).Sometimes the term "Archimedean spiral" is used for the more general group of spirals

The normal Archimedean spiral occurs when "c" = 1.Other spirals falling into this group include the hyperbolic spiral ("c" = −1), Fermat's spiral ("c" = 2), and the lituus ("c" = −2).