Quote Originally Posted by Mr. Widget View Post
<snip> ... and hear it in everyday conversations. This is a misnomer, isn't it? ... <snip>
<snip> ... that it affects dispersion characteristics but doesn't act as a true ...<snip>
Yes, it is a missnomer. There are many more: just think about all those CD horns named "biradial", though their construction may be completely different, such as Manta Ray.

"Dispersion" is the dependency of wave properties on the wavelength, e.g. the dependency of the speed of light in glass on the wavelength. In an optical lense this leads to an error called "chromatic aberration".

Ruediger