In the English kinship system, a first cousin is defined as the child of one's parent's sibling. More broadly, the term "cousin" encompasses relatives who share a common ancestor and are separated by two or more generations. To precisely describe these relationships, "degree" measures the generational distance from the common ancestor, while "removal" indicates any difference in generations between the cousins.

This comprehensive definition means individuals can have significantly more living cousins than any other type of relative, with genealogists sometimes tracking hundreds across centuries. Additional terms like "cousin-uncle/aunt" specify generational differences, and a "grandcousin" refers to a first cousin twice removed, highlighting the varied and extensive nature of these family connections.