One of the first thing you read about when learning about geodesic domes is the term “frequency”. It’s quite simple to understand, actually.
Think of geodesic frequency as density. The higher the frequency, the more struts are used. In real life this means there are more triangles in the same dome.
Look at the image below. The same base triangle is divided further every time you increase the frequency.
The frequency of a geodesic dome indicates how many times each side of the base triangle is subdivided. For example frequency 3 means the base triangle is divided into 3 sections (or triangles) on each side.
So why use different frequencies?
The answer is two-fold: first the higher the frequency, the rounder the dome becomes. Second reason is strength of the structure.
The average greenhouse for instance is more than adequate with a 3V frame. In cases for large domes or homes, 5V or 6V are often chosen when constructing very large domes and for their resistance to snow and wind loads.