Collateral Degree.

The system of collateral degree or removal involves the least number of degree calculations and focuses on identifying genealogical relationships in reference to a core ancestral line and its collateral offshoots. (See Lineal and Collateral Kin.) It can be formally defined as the lesser of the number of links that each of two relatives (Ego and Alter) traces to his/her most recent common ancestor.

The number determining collateral degree is calculated as the lesser of the number of links that either Ego or Alter can trace back to his/her most recent common ancestor.
In this case,

Ego counts 4 links,
Alter counts 3 links,
the collateral degree is 3, the lesser of the two numbers.

The following diagram diplays the standard pattern of collateral degree calculation

Collateral Degree Numbering

How to count cousins

Collateral degree calculation is inherent in the English differentiation of cousin types, i.e. first cousins are all of the second collateral degree, second cousins of the third degree, ... nth cousin of the (n+1)th degree. Degrees of removal (once removed, twice removed, etc.) refer to generation differences. Thus a first cousin of Ego's father's generation would be Ego's first cousin once removed.

Cousin Degree and Removal

This is the last screen on kinship degree.