What is Geodesic Dome Frequency?

Dome Frequency is denoted by the letter "v".

"2v" is short for "2 frequency". A 2v dome is a 2 frequency dome, and a 3v dome is a 3 frequency dome. 2 frequency has two different lengths and 3 frequency has three different lengths. 

The short explanation for dome frequency is, the higher the "v", or frequency, the more triangles there are in the geodesic dome. A higher frequency dome with more triangles will be stronger and more spherical than a lower frequency dome, and the higher frequency dome will be more complicated to build, as it will have more struts.

Reference: https://www.ziptiedomes.com/