The present invention relates to airfoils and design and design optimization of airfoils, in particular airfoils of rotor blades for wind turbines. One aspect of the invention relates to an airfoil with an external shape provided by an airfoil profile defined by a limited number of parameters, such as a set of parameters. Another aspect of the invention relates to a method for designing an airfoil by means of an analytical airfoil profile, said method comprising the step of applying a conformal mapping to a near circle in a near circle plane, wherein the near circle is at least partly expressed by means of an analytical function, said conformal mapping transforming the near circle in the near circle plane to the airfoil profile in an airfoil plane. L