Counting cousins - explaining second, third, and fourth cousins. {}
AncestryDNA® can match you with your cousins with a high degree of accuracy with a simple DNA test. You may discover many of your 4th and 5th cousins—and sometimes even your 8th or 10th cousins. { it depends / ymmv }

What does the match confidence score mean? {}

Understanding Kinship Terms {}
A direct ancestor is anyone you descend from. You descend from your parents, who descend from their parents, who descend from their parents, and so on. That chain of parents and children are your direct ancestors. Not every older relative is your direct ancestor. For example, your aunts and uncles are not your direct ancestors, because you don’t descend from them. A common ancestor is someone {a direct ancestor} you and a relative, e.g., a DNA Match, both descend from. Note: ancestry Pedigree view displays a tree horizontally, with descendants on the left and direct ancestors to the right.

How Many Centimorgans Do You Share With Your Relatives? {}

Cousin Calculator {}

Estimating Relationships from Shared DNA {}

AncestryDNA Matching White Paper {}

The Shared cM Project - Version 4.0 - March 2020 {pdf -}

The Shared cM Project - Version 4.0 - March 2020 {image -}

Why DNA Testing the Oldest Family Members is Critically Important